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Correct documentation of initial/inherit values and of last boolean in CheckPropertyData. Note that document misses modifications to nsDOMCSSDeclaration and relevant interfaces. Massive formatting cleanup (especially <br> overuse), but not enough.

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git-svn-id: svn://10.0.0.236/trunk@123565 18797224-902f-48f8-a5cc-f745e15eee43
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dbaron%fas.harvard.edu 2002-06-19 04:29:07 +00:00
parent 438ada5443
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mozilla/layout/doc/adding-style-props.html
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@ -4,68 +4,70 @@
<body>
<h1>Adding a new style property</h1>
<br>
<blockquote>
<h4>Document history:</h4>
<ul>
<li>03/21/2001: Marc Attinasi (attinasi@netscape.com) created document
<li>03/21/2002: Marc Attinasi (attinasi@netscape.com) created document
/ implementing -moz-force-broken-image-icon for bug <a href="http://bugzilla.mozilla.org/show_bug.cgi?id=58646">
58646</a>
<br>
58646</a></li>
<li>
6/18/2002: David Baron (dbaron@fas.harvard.edu): corrected support
for 'inherit' and '-moz-initial' (didn't test with code, though),
and explained what the final boolean in CheckPropertyData is for.
<li>NOTE: This document is still missing a few pieces. I need to
add information on adding to <code>nsIDOM[NS]CSS2Properties</code>
and <code>nsDOMCSSDeclaration</code>.
</li>
</ul>
</blockquote>
<br>
<h4> </h4>
<h2>Overview</h2>
When a new style property is needed there are many places in the code that
need to be updated. This document outlines the proceedure used to add a new
property, in this case the property is a proprietary one called '-moz-force-broken-image-icons'
and is used as a way for a stylesheet to force broken image icons to be displayed.
This is all being done in the context of <a href="http://bugzilla.mozilla.org/show_bug.cgi?id=58646">
bug 58646</a>
.<br>
bug 58646</a>.
<h2>Analysis</h2>
Up front you have to decide some things about the new property:<br>
<br>
<b>Questions:</b><br>
<p>Up front you have to decide some things about the new property:</p>
<p><b>Questions:</b></p>
<ol>
<li>Is the property proprietary or specified by the CSS standard?<br>
</li>
<li>Is the property proprietary or specified by the CSS standard?</li>
<li>Is the property inherited?</li>
<li>What types of values can the property have?<br>
</li>
<li>What types of values can the property have?</li>
<li>Does it logically fit with other existing properties?</li>
<li>What is the impact to the layout of a page if that property changes?</li>
<li>What do you want to name it?</li>
</ol>
<b>Answers:</b><br>
<p><b>Answers:</b></p>
<ol>
<li>In our specific case, we want a property that is used internally,
so it is a proprietary property.  </li>
so it is a proprietary property.</li>
<li>The property is to be used for images, which are leaf elements, so
there is no need to inherit it. </li>
there is no need to inherit it.</li>
<li>The property is used simply to force a broken image to be represented
by an icon, so it only supports the values '0' and '1' as numerics. </li>
<li>It is hard to see how this property fits logically in with other
properties, but if we stretch our imaginations we could say that it is a
sort of UI property. </li>
sort of UI property.</li>
<li>If this property changes, the image frame has to be recreated. This
is because the decision about whether to display the icon or not will impact
the decision to replace the image frame with an inline text frame for the
ALT text, so if the ALT text inline is already made, there is no image frame
left around to reflow or otherwise modify. </li>
left around to reflow or otherwise modify.</li>
<li>Finally, the name will be '-moz-force-broken-image-icons' - that
should be pretty self-describing (by convention we start proprietary property
names with '-moz-').</li>
</ol>
<h2>Implementation</h2>
There are several places that need to be educated about a new style property.
The are:<br>
<p>There are several places that need to be educated about a new style property.
They are:
</p>
<ul>
<li>CSS Property Names and Hint Tables: the new property name must be
made formally know to the system<br>
</li>
made formally know to the system</li>
<li>CSS Declaration: the declaration must be able to hold the property
and its value(s)</li>
<li>CSS Parser: the parser must be able to parse the property name, validate
@ -80,20 +82,24 @@ and how it is shared by other elements.</li>
words, the meaning of the property.</li>
</ul>
<h3>CSS Property Name / Constants / Hints</h3>
<p>
First, add the new name to the property list in <a href="http://lxr.mozilla.org/seamonkey/source/content/shared/public/nsCSSPropList.h">
nsCSSPropList.h</a>
 Insert the property in the list alphabetically, using the existing
property names as a template. The format of the entry you will create is:
</p>
<pre>CSS_PROP(-moz-force-broken-image-iconst, force_broken_image_icons, FRAMECHANGE) // bug 58646</pre>
The first value is the formal property name, in other words the property
<p>The first value is the formal property name, in other words the property
name as it is seen by the CSS parser.<br>
The second value is the name of the property as it will appear internally.<br>
The last value indicates what must change when the value of the property
changes. It should be one of (<a href="http://lxr.mozilla.org/seamonkey/source/layout/base/public/nsStyleConsts.h#46">
VISUAL, AURAL, REFLOW, CONTENT, FRAMECHANGE</a>
).<br>
<br>
If you need to introduce new constants for the values of the property, they
).</p>
<p>If you need to introduce new constants for the values of the property, they
must be added to <a href="http://lxr.mozilla.org/seamonkey/source/layout/base/public/nsStyleConsts.h">
nsStyleConsts.h</a>
and to the appropriate keyword tables in <a href="http://lxr.mozilla.org/seamonkey/source/content/shared/src/nsCSSProps.cpp">
@ -122,13 +128,115 @@ to (or create a new section if you are creating a new style struct). For
this example we will find the 'UserInterface' section and add our new property
<a href="#AppendValueCase">there</a>
.<br>
<pre> // nsCSSUserInterface<br> case eCSSProperty_user_input:<br> case eCSSProperty_user_modify:<br> case eCSSProperty_user_select:<br> case eCSSProperty_key_equivalent:<br> case eCSSProperty_user_focus:<br> case eCSSProperty_resizer:<br> case eCSSProperty_cursor:<br> case eCSSProperty_force_broken_image_icons: {<br> CSS_ENSURE(UserInterface) {<br> switch (aProperty) {<br> case eCSSProperty_user_input: theUserInterface-&gt;mUserInput = aValue; break;<br> case eCSSProperty_user_modify: theUserInterface-&gt;mUserModify = aValue; break;<br> case eCSSProperty_user_select: theUserInterface-&gt;mUserSelect = aValue; break;<br> case eCSSProperty_key_equivalent: <br> CSS_ENSURE_DATA(theUserInterface-&gt;mKeyEquivalent, nsCSSValueList) {<br> theUserInterface-&gt;mKeyEquivalent-&gt;mValue = aValue;<br> CSS_IF_DELETE(theUserInterface-&gt;mKeyEquivalent-&gt;mNext);<br> }<br> break;<br> case eCSSProperty_user_focus: theUserInterface-&gt;mUserFocus = aValue; break;<br> case eCSSProperty_resizer: theUserInterface-&gt;mResizer = aValue; break;<br> case eCSSProperty_cursor:<br> CSS_ENSURE_DATA(theUserInterface-&gt;mCursor, nsCSSValueList) {<br> theUserInterface-&gt;mCursor-&gt;mValue = aValue;<br> CSS_IF_DELETE(theUserInterface-&gt;mCursor-&gt;mNext);<br> }<br> break;<br><b> <a name="AppendValueCase"></a>case eCSSProperty_force_broken_image_icons: theUserInterface-&gt;mForceBrokenImageIcon = aValue; break;<br></b><br> CSS_BOGUS_DEFAULT; // make compiler happy<br> }<br> }<br> break;<br> }<br><br></pre>
<pre> // nsCSSUserInterface
case eCSSProperty_user_input:
case eCSSProperty_user_modify:
case eCSSProperty_user_select:
case eCSSProperty_key_equivalent:
case eCSSProperty_user_focus:
case eCSSProperty_resizer:
case eCSSProperty_cursor:
case eCSSProperty_force_broken_image_icons: {
CSS_ENSURE(UserInterface) {
switch (aProperty) {
case eCSSProperty_user_input: theUserInterface-&gt;mUserInput = aValue; break;
case eCSSProperty_user_modify: theUserInterface-&gt;mUserModify = aValue; break;
case eCSSProperty_user_select: theUserInterface-&gt;mUserSelect = aValue; break;
case eCSSProperty_key_equivalent:
CSS_ENSURE_DATA(theUserInterface-&gt;mKeyEquivalent, nsCSSValueList) {
theUserInterface-&gt;mKeyEquivalent-&gt;mValue = aValue;
CSS_IF_DELETE(theUserInterface-&gt;mKeyEquivalent-&gt;mNext);
}
break;
case eCSSProperty_user_focus: theUserInterface-&gt;mUserFocus = aValue; break;
case eCSSProperty_resizer: theUserInterface-&gt;mResizer = aValue; break;
case eCSSProperty_cursor:
CSS_ENSURE_DATA(theUserInterface-&gt;mCursor, nsCSSValueList) {
theUserInterface-&gt;mCursor-&gt;mValue = aValue;
CSS_IF_DELETE(theUserInterface-&gt;mCursor-&gt;mNext);
}
break;
<b> <a name="AppendValueCase"></a>case eCSSProperty_force_broken_image_icons: theUserInterface-&gt;mForceBrokenImageIcon = aValue; break;
</b>
CSS_BOGUS_DEFAULT; // make compiler happy
}
}
break;
}
</pre>
The GetValue method must be similarly <a href="#GetValueCase">modified</a>
:<br>
<pre> // nsCSSUserInterface<br> case eCSSProperty_user_input:<br> case eCSSProperty_user_modify:<br> case eCSSProperty_user_select:<br> case eCSSProperty_key_equivalent:<br> case eCSSProperty_user_focus:<br> case eCSSProperty_resizer:<br> case eCSSProperty_cursor:<br> case eCSSProperty_force_broken_image_icons: {<br> CSS_VARONSTACK_GET(UserInterface);<br> if (nsnull != theUserInterface) {<br> switch (aProperty) {<br> case eCSSProperty_user_input: aValue = theUserInterface-&gt;mUserInput; break;<br> case eCSSProperty_user_modify: aValue = theUserInterface-&gt;mUserModify; break;<br> case eCSSProperty_user_select: aValue = theUserInterface-&gt;mUserSelect; break;<br> case eCSSProperty_key_equivalent:<br> if (nsnull != theUserInterface-&gt;mKeyEquivalent) {<br> aValue = theUserInterface-&gt;mKeyEquivalent-&gt;mValue;<br> }<br> break;<br> case eCSSProperty_user_focus: aValue = theUserInterface-&gt;mUserFocus; break;<br> case eCSSProperty_resizer: aValue = theUserInterface-&gt;mResizer; break;<br> case eCSSProperty_cursor:<br> if (nsnull != theUserInterface-&gt;mCursor) {<br> aValue = theUserInterface-&gt;mCursor-&gt;mValue;<br> }<br> break;<br><b> <a name="GetValueCase"></a>case eCSSProperty_force_broken_image_icons: aValue = theUserInterface-&gt;mForceBrokenImageIcons; break;<br></b><br> CSS_BOGUS_DEFAULT; // make compiler happy<br> }<br> }<br> else {<br> aValue.Reset();<br> }<br> break;<br> }<br><br></pre>
<pre> // nsCSSUserInterface
case eCSSProperty_user_input:
case eCSSProperty_user_modify:
case eCSSProperty_user_select:
case eCSSProperty_key_equivalent:
case eCSSProperty_user_focus:
case eCSSProperty_resizer:
case eCSSProperty_cursor:
case eCSSProperty_force_broken_image_icons: {
CSS_VARONSTACK_GET(UserInterface);
if (nsnull != theUserInterface) {
switch (aProperty) {
case eCSSProperty_user_input: aValue = theUserInterface-&gt;mUserInput; break;
case eCSSProperty_user_modify: aValue = theUserInterface-&gt;mUserModify; break;
case eCSSProperty_user_select: aValue = theUserInterface-&gt;mUserSelect; break;
case eCSSProperty_key_equivalent:
if (nsnull != theUserInterface-&gt;mKeyEquivalent) {
aValue = theUserInterface-&gt;mKeyEquivalent-&gt;mValue;
}
break;
case eCSSProperty_user_focus: aValue = theUserInterface-&gt;mUserFocus; break;
case eCSSProperty_resizer: aValue = theUserInterface-&gt;mResizer; break;
case eCSSProperty_cursor:
if (nsnull != theUserInterface-&gt;mCursor) {
aValue = theUserInterface-&gt;mCursor-&gt;mValue;
}
break;
<b> <a name="GetValueCase"></a>case eCSSProperty_force_broken_image_icons: aValue = theUserInterface-&gt;mForceBrokenImageIcons; break;
</b>
CSS_BOGUS_DEFAULT; // make compiler happy
}
}
else {
aValue.Reset();
}
break;
}
</pre>
Finally <a href="#ListCase">modify </a>
the 'List' method to output the property value.<br>
<pre>void nsCSSUserInterface::List(FILE* out, PRInt32 aIndent) const<br>{<br> for (PRInt32 index = aIndent; --index &gt;= 0; ) fputs(" ", out);<br><br> nsAutoString buffer;<br><br> mUserInput.AppendToString(buffer, eCSSProperty_user_input);<br> mUserModify.AppendToString(buffer, eCSSProperty_user_modify);<br> mUserSelect.AppendToString(buffer, eCSSProperty_user_select);<br> nsCSSValueList* keyEquiv = mKeyEquivalent;<br> while (nsnull != keyEquiv) {<br> keyEquiv-&gt;mValue.AppendToString(buffer, eCSSProperty_key_equivalent);<br> keyEquiv= keyEquiv-&gt;mNext;<br> }<br> mUserFocus.AppendToString(buffer, eCSSProperty_user_focus);<br> mResizer.AppendToString(buffer, eCSSProperty_resizer);<br> <br> nsCSSValueList* cursor = mCursor;<br> while (nsnull != cursor) {<br> cursor-&gt;mValue.AppendToString(buffer, eCSSProperty_cursor);<br> cursor = cursor-&gt;mNext;<br> }<br><br> <b> <a name="ListCase"></a>mForceBrokenImageIcon.AppendToString(buffer,eCSSProperty_force_broken_image_icons);</b><br><br> fputs(NS_LossyConvertUCS2toASCII(buffer).get(), out);<br>}<br><br></pre>
<pre>void nsCSSUserInterface::List(FILE* out, PRInt32 aIndent) const
{
for (PRInt32 index = aIndent; --index &gt;= 0; ) fputs(" ", out);
nsAutoString buffer;
mUserInput.AppendToString(buffer, eCSSProperty_user_input);
mUserModify.AppendToString(buffer, eCSSProperty_user_modify);
mUserSelect.AppendToString(buffer, eCSSProperty_user_select);
nsCSSValueList* keyEquiv = mKeyEquivalent;
while (nsnull != keyEquiv) {
keyEquiv-&gt;mValue.AppendToString(buffer, eCSSProperty_key_equivalent);
keyEquiv= keyEquiv-&gt;mNext;
}
mUserFocus.AppendToString(buffer, eCSSProperty_user_focus);
mResizer.AppendToString(buffer, eCSSProperty_resizer);
nsCSSValueList* cursor = mCursor;
while (nsnull != cursor) {
cursor-&gt;mValue.AppendToString(buffer, eCSSProperty_cursor);
cursor = cursor-&gt;mNext;
}
<b> <a name="ListCase"></a>mForceBrokenImageIcon.AppendToString(buffer,eCSSProperty_force_broken_image_icons);</b>
fputs(NS_LossyConvertUCS2toASCII(buffer).get(), out);
}
</pre>
<h3>CSS Parser</h3>
Next, the CSSParser must be educated about this new property so that it can
@ -171,14 +279,54 @@ however there is also a class nsStyleUIReset that holds the non-inherited
values, so we will use that one (remember, our property is not inherited).
Add a <a href="#StyleContextMember">data member</a>
to hold the value:
<pre>struct nsStyleUIReset: public nsStyleStruct {<br> nsStyleUIReset(void);<br> nsStyleUIReset(const nsStyleUIReset&amp; aOther);<br> ~nsStyleUIReset(void);<br><br> NS_DEFINE_STATIC_STYLESTRUCTID_ACCESSOR(eStyleStruct_UIReset)<br><br> void* operator new(size_t sz, nsIPresContext* aContext) {<br> void* result = nsnull;<br> aContext-&gt;AllocateFromShell(sz, &amp;result);<br> return result;<br> }<br> void Destroy(nsIPresContext* aContext) {<br> this-&gt;~nsStyleUIReset();<br> aContext-&gt;FreeToShell(sizeof(nsStyleUIReset), this);<br> };<br><br> PRInt32 CalcDifference(const nsStyleUIReset&amp; aOther) const;<br><br> PRUint8 mUserSelect; // [reset] (selection-style)<br> PRUnichar mKeyEquivalent; // [reset] XXX what type should this be?<br> PRUint8 mResizer; // [reset]<br> <b><a name="StyleContextMember"></a>PRUint8 mForceBrokenImageIcon; // [reset] (0 if not forcing, otherwise forcing)</b><br>};<br></pre>
<pre>struct nsStyleUIReset: public nsStyleStruct {
nsStyleUIReset(void);
nsStyleUIReset(const nsStyleUIReset&amp; aOther);
~nsStyleUIReset(void);
NS_DEFINE_STATIC_STYLESTRUCTID_ACCESSOR(eStyleStruct_UIReset)
void* operator new(size_t sz, nsIPresContext* aContext) {
void* result = nsnull;
aContext-&gt;AllocateFromShell(sz, &amp;result);
return result;
}
void Destroy(nsIPresContext* aContext) {
this-&gt;~nsStyleUIReset();
aContext-&gt;FreeToShell(sizeof(nsStyleUIReset), this);
};
PRInt32 CalcDifference(const nsStyleUIReset&amp; aOther) const;
PRUint8 mUserSelect; // [reset] (selection-style)
PRUnichar mKeyEquivalent; // [reset] XXX what type should this be?
PRUint8 mResizer; // [reset]
<b><a name="StyleContextMember"></a>PRUint8 mForceBrokenImageIcon; // [reset] (0 if not forcing, otherwise forcing)</b>
};
</pre>
In the implementation file <a href="http://lxr.mozilla.org/seamonkey/source/content/shared/src/nsStyleStruct.cpp">
nsStyleContext.cpp </a>
add the new data member to the constructors of the style struct and the CalcDifference
method, which must return the correct style-change hint when a change to
your new property is detected. The constructor changes are obvious, but here
is the CalcDifference change for our example:<br>
<pre>PRInt32 nsStyleUIReset::CalcDifference(const nsStyleUIReset&amp; aOther) const<br>{<br> <b> if (mForceBrokenImageIcon == aOther.mForceBrokenImageIcon) {</b><br> if (mResizer == aOther.mResizer) {<br> if (mUserSelect == aOther.mUserSelect) {<br> if (mKeyEquivalent == aOther.mKeyEquivalent) {<br> return NS_STYLE_HINT_NONE;<br> }<br> return NS_STYLE_HINT_CONTENT;<br> }<br> return NS_STYLE_HINT_VISUAL;<br> }<br> return NS_STYLE_HINT_VISUAL;<br> }<br> <b>return NS_STYLE_HINT_FRAMECHANGE;<br></b>}<br></pre>
<pre>PRInt32 nsStyleUIReset::CalcDifference(const nsStyleUIReset&amp; aOther) const
{
<b> if (mForceBrokenImageIcon == aOther.mForceBrokenImageIcon) {</b>
if (mResizer == aOther.mResizer) {
if (mUserSelect == aOther.mUserSelect) {
if (mKeyEquivalent == aOther.mKeyEquivalent) {
return NS_STYLE_HINT_NONE;
}
return NS_STYLE_HINT_CONTENT;
}
return NS_STYLE_HINT_VISUAL;
}
return NS_STYLE_HINT_VISUAL;
}
<b>return NS_STYLE_HINT_FRAMECHANGE;
</b>}
</pre>
<h3>CSSStyleRule</h3>
The nsCSSStyleRule must be updated to manage mapping the declaration to the
style struct. In the file <a href="http://lxr.mozilla.org/seamonkey/source/content/html/style/src/nsCSSStyleRule.cpp">
@ -187,21 +335,109 @@ nsCSSStyleRule.cpp</a>
you have added your property to. For example, we <a href="http://bugzilla.mozilla.org/MapUIForDeclChange">
update </a>
MapUIForDeclaration:<br>
<pre>static nsresult<br>MapUIForDeclaration(nsCSSDeclaration* aDecl, const nsStyleStructID&amp; aID, nsCSSUserInterface&amp; aUI)<br>{<br> if (!aDecl)<br> return NS_OK; // The rule must have a declaration.<br><br> nsCSSUserInterface* ourUI = (nsCSSUserInterface*)aDecl-&gt;GetData(kCSSUserInterfaceSID);<br> if (!ourUI)<br> return NS_OK; // We don't have any rules for UI.<br><br> if (aID == eStyleStruct_UserInterface) {<br> if (aUI.mUserFocus.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserFocus.GetUnit() != eCSSUnit_Null)<br> aUI.mUserFocus = ourUI-&gt;mUserFocus;<br> <br> if (aUI.mUserInput.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserInput.GetUnit() != eCSSUnit_Null)<br> aUI.mUserInput = ourUI-&gt;mUserInput;<br><br> if (aUI.mUserModify.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserModify.GetUnit() != eCSSUnit_Null)<br> aUI.mUserModify = ourUI-&gt;mUserModify;<br><br> if (!aUI.mCursor &amp;&amp; ourUI-&gt;mCursor)<br> aUI.mCursor = ourUI-&gt;mCursor;<br><br><br> }<br> else if (aID == eStyleStruct_UIReset) {<br> if (aUI.mUserSelect.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserSelect.GetUnit() != eCSSUnit_Null)<br> aUI.mUserSelect = ourUI-&gt;mUserSelect;<br> <br> if (!aUI.mKeyEquivalent &amp;&amp; ourUI-&gt;mKeyEquivalent)<br> aUI.mKeyEquivalent = ourUI-&gt;mKeyEquivalent;<br><br> if (aUI.mResizer.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mResizer.GetUnit() != eCSSUnit_Null)<br> aUI.mResizer = ourUI-&gt;mResizer;<br> <b><br> <a name="MapUIForDeclChange"></a>if (aUI.mForceBrokenImageIcon.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mForceBrokenImageIcon.GetUnit() == eCSSUnit_Integer)<br> aUI.mForceBrokenImageIcon = ourUI-&gt;mForceBrokenImageIcon;</b><br> }<br><br> return NS_OK;<br><br>}<br></pre>
<pre>static nsresult
MapUIForDeclaration(nsCSSDeclaration* aDecl, const nsStyleStructID&amp; aID, nsCSSUserInterface&amp; aUI)
{
if (!aDecl)
return NS_OK; // The rule must have a declaration.
nsCSSUserInterface* ourUI = (nsCSSUserInterface*)aDecl-&gt;GetData(kCSSUserInterfaceSID);
if (!ourUI)
return NS_OK; // We don't have any rules for UI.
if (aID == eStyleStruct_UserInterface) {
if (aUI.mUserFocus.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserFocus.GetUnit() != eCSSUnit_Null)
aUI.mUserFocus = ourUI-&gt;mUserFocus;
if (aUI.mUserInput.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserInput.GetUnit() != eCSSUnit_Null)
aUI.mUserInput = ourUI-&gt;mUserInput;
if (aUI.mUserModify.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserModify.GetUnit() != eCSSUnit_Null)
aUI.mUserModify = ourUI-&gt;mUserModify;
if (!aUI.mCursor &amp;&amp; ourUI-&gt;mCursor)
aUI.mCursor = ourUI-&gt;mCursor;
}
else if (aID == eStyleStruct_UIReset) {
if (aUI.mUserSelect.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mUserSelect.GetUnit() != eCSSUnit_Null)
aUI.mUserSelect = ourUI-&gt;mUserSelect;
if (!aUI.mKeyEquivalent &amp;&amp; ourUI-&gt;mKeyEquivalent)
aUI.mKeyEquivalent = ourUI-&gt;mKeyEquivalent;
if (aUI.mResizer.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mResizer.GetUnit() != eCSSUnit_Null)
aUI.mResizer = ourUI-&gt;mResizer;
<b>
<a name="MapUIForDeclChange"></a>if (aUI.mForceBrokenImageIcon.GetUnit() == eCSSUnit_Null &amp;&amp; ourUI-&gt;mForceBrokenImageIcon.GetUnit() == eCSSUnit_Integer)
aUI.mForceBrokenImageIcon = ourUI-&gt;mForceBrokenImageIcon;</b>
}
return NS_OK;
}
</pre>
<h3>Rule Node</h3>
Now we have to update the RuleNode code to know about the new property. First,
locate the PropertyCheckData array for the data that you added the new property
to. For this example, we add the following:<br>
<pre>static const PropertyCheckData UIResetCheckProperties[] = {<br> CHECKDATA_PROP(nsCSSUserInterface, mUserSelect, CHECKDATA_VALUE, PR_FALSE),<br> CHECKDATA_PROP(nsCSSUserInterface, mResizer, CHECKDATA_VALUE, PR_FALSE),<br> CHECKDATA_PROP(nsCSSUserInterface, mKeyEquivalent, CHECKDATA_VALUELIST, PR_FALSE)<br> <b>CHECKDATA_PROP(nsCSSUserInterface, mForceBrokenImageIcon, CHECKDATA_VALUE, PR_FALSE)</b><br>};<br></pre>
<pre>static const PropertyCheckData UIResetCheckProperties[] = {
CHECKDATA_PROP(nsCSSUserInterface, mUserSelect, CHECKDATA_VALUE, PR_FALSE),
CHECKDATA_PROP(nsCSSUserInterface, mResizer, CHECKDATA_VALUE, PR_FALSE),
CHECKDATA_PROP(nsCSSUserInterface, mKeyEquivalent, CHECKDATA_VALUELIST, PR_FALSE)
<b>CHECKDATA_PROP(nsCSSUserInterface, mForceBrokenImageIcon, CHECKDATA_VALUE, PR_FALSE)</b>
};
</pre>
The first two arguments correspond to the structure and data member from
teh CSSDeclaration, the third is the data type, the fourth indicates if it
is a coord value or not.<br>
the CSSDeclaration, the third is the data type, the fourth indicates
whether it is a coord value that uses an explicit inherit value on the
style data struct that must be computed by layout.<br>
<br>
Next, we have to make sure the ComputeXXX method for the structure the property
was added to is updated to mange the new value. In this example we need to
modify the nsRuleNode::ComputeUIResetData method to handle the CSS Declaration
to the style struct:<br>
<pre> ...<br> // resizer: auto, none, enum, inherit<br> if (eCSSUnit_Enumerated == uiData.mResizer.GetUnit()) {<br> ui-&gt;mResizer = uiData.mResizer.GetIntValue();<br> }<br> else if (eCSSUnit_Auto == uiData.mResizer.GetUnit()) {<br> ui-&gt;mResizer = NS_STYLE_RESIZER_AUTO;<br> }<br> else if (eCSSUnit_None == uiData.mResizer.GetUnit()) {<br> ui-&gt;mResizer = NS_STYLE_RESIZER_NONE;<br> }<br> else if (eCSSUnit_Inherit == uiData.mResizer.GetUnit()) {<br> inherited = PR_TRUE;<br> ui-&gt;mResizer = parentUI-&gt;mResizer;<br> }<br><br> <b>// force-broken-image-icons: integer<br> if (eCSSUnit_Integer == uiData.mForceBrokenImageIcons.GetUnit()) {<br> ui-&gt;mForceBrokenImageIcons = uiData.mForceBrokenImageIcons.GetIntValue();<br> }</b><br> <br> if (inherited)<br> // We inherited, and therefore can't be cached in the rule node. We have to be put right on the<br> // style context.<br> aContext-&gt;SetStyle(eStyleStruct_UIReset, *ui);<br> else {<br> // We were fully specified and can therefore be cached right on the rule node.<br> if (!aHighestNode-&gt;mStyleData.mResetData)<br> aHighestNode-&gt;mStyleData.mResetData = new (mPresContext) nsResetStyleData;<br> aHighestNode-&gt;mStyleData.mResetData-&gt;mUIData = ui;<br> // Propagate the bit down.<br> PropagateDependentBit(NS_STYLE_INHERIT_UI_RESET, aHighestNode);<br> }<br> ...<br></pre>
<pre> ...
// resizer: auto, none, enum, inherit
if (eCSSUnit_Enumerated == uiData.mResizer.GetUnit()) {
ui-&gt;mResizer = uiData.mResizer.GetIntValue();
}
else if (eCSSUnit_Auto == uiData.mResizer.GetUnit()) {
ui-&gt;mResizer = NS_STYLE_RESIZER_AUTO;
}
else if (eCSSUnit_None == uiData.mResizer.GetUnit()) {
ui-&gt;mResizer = NS_STYLE_RESIZER_NONE;
}
else if (eCSSUnit_Inherit == uiData.mResizer.GetUnit()) {
inherited = PR_TRUE;
ui-&gt;mResizer = parentUI-&gt;mResizer;
}
<b>// force-broken-image-icons: integer, inherit, -moz-initial
if (eCSSUnit_Integer == uiData.mForceBrokenImageIcons.GetUnit()) {
ui-&gt;mForceBrokenImageIcons = uiData.mForceBrokenImageIcons.GetIntValue();
} else if (eCSSUnit_Inherit == uiData.mForceBrokenImageIcons.GetUnit()) {
inherited = PR_TRUE;
ui-&gt;mForceBrokenImageIcons = parentUI-&gt;mForceBrokenImageIcons;
} else if (eCSSUnit_Initial == uiData.mForceBrokenImageIcons.GetUnit()) {
ui-&gt;mForceBrokenImageIcons = 0;
}</b>
if (inherited)
// We inherited, and therefore can't be cached in the rule node. We have to be put right on the
// style context.
aContext-&gt;SetStyle(eStyleStruct_UIReset, *ui);
else {
// We were fully specified and can therefore be cached right on the rule node.
if (!aHighestNode-&gt;mStyleData.mResetData)
aHighestNode-&gt;mStyleData.mResetData = new (mPresContext) nsResetStyleData;
aHighestNode-&gt;mStyleData.mResetData-&gt;mUIData = ui;
// Propagate the bit down.
PropagateDependentBit(NS_STYLE_INHERIT_UI_RESET, aHighestNode);
}
...
</pre>
<h3>Layout</h3>
OK, finally the style system is supporting the new property. It is time to
actually make use of it now.<br>
@ -209,10 +445,18 @@ actually make use of it now.<br>
In layout, retrieve the styleStruct that has the new property from the frame's
style context. Access the new property and get its value. It is that simple.
For this example, it looks like this, in nsImageFrame:<br>
<pre> PRBool forceIcon = PR_FALSE;<br><br> const nsStyleUIReset* styleData;<br> GetStyleData(eStyleStruct_UIReset, (const nsStyleStruct*&amp;) styleData);<br> if (styleData-&gt;mForceBrokenImageIcon) {<br> forceIcon = PR_TRUE;<br> }<br><br></pre>
<pre> PRBool forceIcon = PR_FALSE;
const nsStyleUIReset* styleData;
GetStyleData(eStyleStruct_UIReset, (const nsStyleStruct*&amp;) styleData);
if (styleData-&gt;mForceBrokenImageIcon) {
forceIcon = PR_TRUE;
}
</pre>
Create some testcases with style rules that use the new property, make sure
it is being parsed correctly. Test it in an external stylesheet and in inline
style. Test that it is inherited correctly, or not inherited as appropriate
to your property. Update this document with any further details, or correcting
any errors.<br>
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