Bug 395564 - "scrollbar's arrow buttons should be disabled when they can't scroll further" [p=twanno@lycos.nl (Teune van Steeg) r+sr=roc a1.9=schrep]

toolkit/content/widgets/scrollbar.xml

@@ -19,18 +19,17 @@
       <handler event="command" action="event.stopPropagation();"/>
     </handlers>
   </binding>
-  
+
   <binding id="scrollbar" extends="chrome://global/content/bindings/scrollbar.xml#scrollbar-base">
     <content>
-      <xul:scrollbarbutton sbattr="scrollbar-up-top" type="decrement" xbl:inherits="disabled,sborient=orient"/>
-      <xul:scrollbarbutton sbattr="scrollbar-down-top" type="increment" xbl:inherits="disabled,sborient=orient"/>
+      <xul:scrollbarbutton sbattr="scrollbar-up-top" type="decrement" xbl:inherits="curpos,maxpos,disabled,sborient=orient"/>
+      <xul:scrollbarbutton sbattr="scrollbar-down-top" type="increment" xbl:inherits="curpos,maxpos,disabled,sborient=orient"/>
       <xul:slider flex="1" xbl:inherits="disabled,curpos,maxpos,pageincrement,increment,orient,sborient=orient">
         <xul:thumb sbattr="scrollbar-thumb" xbl:inherits="orient,sborient=orient,collapsed=disabled" 
                    align="center" pack="center"/>
       </xul:slider>
-      <xul:scrollbarbutton sbattr="scrollbar-up-bottom" type="decrement" xbl:inherits="disabled,sborient=orient"/>
-      <xul:scrollbarbutton sbattr="scrollbar-down-bottom" type="increment" xbl:inherits="disabled,sborient=orient"/>
+      <xul:scrollbarbutton sbattr="scrollbar-up-bottom" type="decrement" xbl:inherits="curpos,maxpos,disabled,sborient=orient"/>
+      <xul:scrollbarbutton sbattr="scrollbar-down-bottom" type="increment" xbl:inherits="curpos,maxpos,disabled,sborient=orient"/>
     </content>
   </binding>
 </bindings>
-

widget/src/gtk2/nsNativeThemeGTK.cpp

@@ -271,14 +271,26 @@ nsNativeThemeGTK::GetGtkWidgetAndState(PRUint8 aWidgetType, nsIFrame* aFrame,
           aState->maxpos = CheckIntAttr(tmpFrame, nsWidgetAtoms::maxpos);
         }
 
-        // In order to simulate native GTK scrollbar click behavior, we set the
-        // active attribute on the element to true if it's pressed with any mouse
-        // button. This allows us to show that it's active without setting :active
         if (aWidgetType == NS_THEME_SCROLLBAR_BUTTON_UP ||
             aWidgetType == NS_THEME_SCROLLBAR_BUTTON_DOWN ||
             aWidgetType == NS_THEME_SCROLLBAR_BUTTON_LEFT ||
             aWidgetType == NS_THEME_SCROLLBAR_BUTTON_RIGHT) {
-          if (CheckBooleanAttr(aFrame, nsWidgetAtoms::active))
+          // set the state to disabled when the scrollbar is scrolled to
+          // the beginning or the end, depending on the button type.
+          PRInt32 curpos = CheckIntAttr(aFrame, nsWidgetAtoms::curpos);
+          PRInt32 maxpos = CheckIntAttr(aFrame, nsWidgetAtoms::maxpos);
+          if ((curpos == 0 && (aWidgetType == NS_THEME_SCROLLBAR_BUTTON_UP ||
+                aWidgetType == NS_THEME_SCROLLBAR_BUTTON_LEFT)) ||
+              (curpos == maxpos &&
+               (aWidgetType == NS_THEME_SCROLLBAR_BUTTON_DOWN ||
+                aWidgetType == NS_THEME_SCROLLBAR_BUTTON_RIGHT)))
+            aState->disabled = PR_TRUE;
+
+          // In order to simulate native GTK scrollbar click behavior,
+          // we set the active attribute on the element to true if it's
+          // pressed with any mouse button.
+          // This allows us to show that it's active without setting :active
+          else if (CheckBooleanAttr(aFrame, nsWidgetAtoms::active))
             aState->active = PR_TRUE;
 
           if (aWidgetFlags) {
@@ -1134,6 +1146,16 @@ nsNativeThemeGTK::WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType,
     return NS_OK;
   }
 
+  if ((aWidgetType == NS_THEME_SCROLLBAR_BUTTON_UP ||
+       aWidgetType == NS_THEME_SCROLLBAR_BUTTON_DOWN ||
+       aWidgetType == NS_THEME_SCROLLBAR_BUTTON_LEFT ||
+       aWidgetType == NS_THEME_SCROLLBAR_BUTTON_RIGHT) &&
+      (aAttribute == nsWidgetAtoms::curpos ||
+       aAttribute == nsWidgetAtoms::maxpos)) {
+    *aShouldRepaint = PR_TRUE;
+    return NS_OK;
+  }
+
   // XXXdwh Not sure what can really be done here.  Can at least guess for
   // specific widgets that they're highly unlikely to have certain states.
   // For example, a toolbar doesn't care about any states.