[GTK] WebKit browser scrollbars not always correctly displayed if ove…

…rlay scrollbars are disabled

https://bugs.webkit.org/show_bug.cgi?id=234874

Patch by Michael Catanzaro <mcatanzaro@gnome.org> on 2022-02-11
Reviewed by Carlos Garcia Campos.

If overlay scrollbars are disabled, and there is not enough content for the page to be
scrollable, and scrollbars are forced using overflow:scroll, then we currently fail to
paint the scrollbars properly. At minimum, we need to paint the scrollbar background, which
is what the macOS port does. Do so.

In the future, we might want to additionally paint the rest of the scrollbars, similar to
the GTK_POLICY_ALWAYS scrollbar policy type, but this would require more work.

* platform/adwaita/ScrollbarThemeAdwaita.cpp:
(WebCore::ScrollbarThemeAdwaita::paint):
* platform/gtk/ScrollbarThemeGtk.cpp:
(WebCore::ScrollbarThemeGtk::paint):


Canonical link: https://commits.webkit.org/247131@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@289620 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,23 @@
+2022-02-11  Michael Catanzaro  <mcatanzaro@gnome.org>
+
+        [GTK] WebKit browser scrollbars not always correctly displayed if overlay scrollbars are disabled
+        https://bugs.webkit.org/show_bug.cgi?id=234874
+
+        Reviewed by Carlos Garcia Campos.
+
+        If overlay scrollbars are disabled, and there is not enough content for the page to be
+        scrollable, and scrollbars are forced using overflow:scroll, then we currently fail to
+        paint the scrollbars properly. At minimum, we need to paint the scrollbar background, which
+        is what the macOS port does. Do so.
+
+        In the future, we might want to additionally paint the rest of the scrollbars, similar to
+        the GTK_POLICY_ALWAYS scrollbar policy type, but this would require more work.
+
+        * platform/adwaita/ScrollbarThemeAdwaita.cpp:
+        (WebCore::ScrollbarThemeAdwaita::paint):
+        * platform/gtk/ScrollbarThemeGtk.cpp:
+        (WebCore::ScrollbarThemeGtk::paint):
+
 2022-02-11  Antti Koivisto  <antti@apple.com>
 
         [CSS Container Queries] Implement container name matching

Source/WebCore/platform/adwaita/ScrollbarThemeAdwaita.cpp

@@ -117,7 +117,7 @@ bool ScrollbarThemeAdwaita::paint(Scrollbar& scrollbar, GraphicsContext& graphic
     if (graphicsContext.paintingDisabled())
         return false;
 
-    if (!scrollbar.enabled())
+    if (!scrollbar.enabled() && usesOverlayScrollbars())
         return true;
 
     IntRect rect = scrollbar.frameRect();

Source/WebCore/platform/gtk/ScrollbarThemeGtk.cpp

@@ -331,7 +331,7 @@ bool ScrollbarThemeGtk::paint(Scrollbar& scrollbar, GraphicsContext& graphicsCon
     if (graphicsContext.paintingDisabled())
         return false;
 
-    if (!scrollbar.enabled())
+    if (!scrollbar.enabled() && usesOverlayScrollbars())
         return true;
 
     double opacity = scrollbar.hoveredPart() == NoPart ? scrollbar.opacity() : 1;
@@ -376,18 +376,20 @@ bool ScrollbarThemeGtk::paint(Scrollbar& scrollbar, GraphicsContext& graphicsCon
     preferredSize += scrollbarGadget.preferredSize() - scrollbarGadget.minimumSize();
 
     FloatRect contentsRect(rect);
-    // When using overlay scrollbars we always claim the size of the scrollbar when hovered, so when
-    // drawing the indicator we need to adjust the rectangle to its actual size in indicator mode.
-    if (scrollbar.orientation() == ScrollbarOrientation::Vertical) {
-        if (rect.width() != preferredSize.width()) {
-            if (!scrollbar.scrollableArea().shouldPlaceVerticalScrollbarOnLeft())
-                contentsRect.move(std::abs(rect.width() - preferredSize.width()), 0);
-            contentsRect.setWidth(preferredSize.width());
-        }
-    } else {
-        if (rect.height() != preferredSize.height()) {
-            contentsRect.move(0, std::abs(rect.height() - preferredSize.height()));
-            contentsRect.setHeight(preferredSize.height());
+    if (usesOverlayScrollbars()) {
+        // When using overlay scrollbars we always claim the size of the scrollbar when hovered, so when
+        // drawing the indicator we need to adjust the rectangle to its actual size in indicator mode.
+        if (scrollbar.orientation() == ScrollbarOrientation::Vertical) {
+            if (rect.width() != preferredSize.width()) {
+                if (!scrollbar.scrollableArea().shouldPlaceVerticalScrollbarOnLeft())
+                    contentsRect.move(std::abs(rect.width() - preferredSize.width()), 0);
+                contentsRect.setWidth(preferredSize.width());
+            }
+        } else {
+            if (rect.height() != preferredSize.height()) {
+                contentsRect.move(0, std::abs(rect.height() - preferredSize.height()));
+                contentsRect.setHeight(preferredSize.height());
+            }
         }
     }