Disable the apply button if the input is invalid

src/main/resources/ocelot/desktop/colorscheme.txt

@@ -58,10 +58,13 @@ TextInputForeground    = #333333
 TextInputBorderError        = #aa8888
 TextInputBorderErrorFocused = #cc6666
 
-ButtonBackground = #aaaaaa
-ButtonBorder     = #888888
-ButtonForeground = #333333
-ButtonConfirm = #336633
+ButtonBackground         = #aaaaaa
+ButtonBorder             = #888888
+ButtonForeground         = #333333
+ButtonBackgroundDisabled = #333333
+ButtonBorderDisabled     = #666666
+ButtonForegroundDisabled = #888888
+ButtonConfirm            = #336633
 
 BottomDrawerBorder = #888888
 

src/main/scala/ocelot/desktop/ui/widget/Button.scala

@@ -11,26 +11,40 @@ import ocelot.desktop.util.DrawUtils
 
 class Button extends Widget with ClickHandler with ClickSoundSource {
   def text: String = ""
+
   def onClick(): Unit = {}
 
+  def enabled: Boolean = true
+
   override def receiveMouseEvents: Boolean = true
 
   eventHandlers += {
-    case ClickEvent(MouseEvent.Button.Left, _) =>
+    case ClickEvent(MouseEvent.Button.Left, _) if enabled =>
       onClick()
 
       clickSoundSource.play()
   }
 
   override def minimumSize: Size2D = Size2D(24 + text.length * 8, 24)
+
   override def maximumSize: Size2D = minimumSize
 
   override def draw(g: Graphics): Unit = {
-    g.rect(bounds, ColorScheme("ButtonBackground"))
-    DrawUtils.ring(g, position.x, position.y, width, height, 2, ColorScheme("ButtonBorder"))
+    val (background, border, foreground) = if (enabled) (
+      ColorScheme("ButtonBackground"),
+      ColorScheme("ButtonBorder"),
+      ColorScheme("ButtonForeground")
+    ) else (
+      ColorScheme("ButtonBackgroundDisabled"),
+      ColorScheme("ButtonBorderDisabled"),
+      ColorScheme("ButtonForegroundDisabled")
+    )
+
+    g.rect(bounds, background)
+    DrawUtils.ring(g, position.x, position.y, width, height, 2, border)
 
     g.background = Color.Transparent
-    g.foreground = ColorScheme("ButtonForeground")
+    g.foreground = foreground
     val textWidth = text.iterator.map(g.font.charWidth(_)).sum
     g.text(position.x + ((width - textWidth) / 2).round, position.y + 4, text)
   }

src/main/scala/ocelot/desktop/ui/widget/ChangeSimulationSpeedDialog.scala

@@ -91,10 +91,10 @@ class ChangeSimulationSpeedDialog() extends ModalDialog {
         override def onClick(): Unit = close()
       }, Padding2D(right = 8))
 
-      // TODO: disable the button if tickInterval.isEmpty
       children :+= new Button {
         override def text: String = "Apply"
         override def onClick(): Unit = confirm()
+        override def enabled: Boolean = tickInterval.nonEmpty
       }
     }
   }, Padding2D.equal(16))