Allow overlay scrolling on GTK, except for GAL canvases.

This prevents glitches when both scrollbars
are visible and scrolling to the end.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/10559

Fixes https://gitlab.com/kicad/code/kicad/-/issues/9988

(cherry picked from commit 4c4089e836)

common/draw_panel_gal.cpp

@@ -94,6 +94,7 @@ EDA_DRAW_PANEL_GAL::EDA_DRAW_PANEL_GAL( wxWindow* aParentWindow, wxWindowID aWin
 
     ShowScrollbars( wxSHOW_SB_ALWAYS, wxSHOW_SB_ALWAYS );
     EnableScrolling( false, false ); // otherwise Zoom Auto disables GAL canvas
+    KIPLATFORM::UI::SetOverlayScrolling( this, false ); // Prevent excessive repaint on GTK
 
     Connect( wxEVT_SIZE, wxSizeEventHandler( EDA_DRAW_PANEL_GAL::onSize ), nullptr, this );
     Connect( wxEVT_ENTER_WINDOW, wxMouseEventHandler( EDA_DRAW_PANEL_GAL::onEnter ), nullptr,

libs/kiplatform/gtk/environment.cpp

@@ -39,10 +39,6 @@ void KIPLATFORM::ENV::Init()
     // required until wxWidgets supports the Wayland compositors
     wxSetEnv( wxT( "GDK_BACKEND" ), wxT( "x11" ) );
 
-    // Disable overlay scrollbars as they mess up wxWidgets window sizing and cause
-    // excessive redraw requests.
-    wxSetEnv( wxT( "GTK_OVERLAY_SCROLLING" ), wxT( "0" ) );
-
     // Set GTK2-style input instead of xinput2.  This disables touchscreen and smooth
     // scrolling.  It's needed to ensure that we are not getting multiple mouse scroll
     // events.

libs/kiplatform/gtk/ui.cpp

@@ -120,3 +120,17 @@ double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
 
     return val;
 }
+
+
+wxSize KIPLATFORM::UI::GetUnobscuredSize( const wxWindow* aWindow )
+{
+    return wxSize( aWindow->GetSize().GetX() - wxSystemSettings::GetMetric( wxSYS_VSCROLL_X ),
+                   aWindow->GetSize().GetY() - wxSystemSettings::GetMetric( wxSYS_HSCROLL_Y ) );
+}
+
+
+void KIPLATFORM::UI::SetOverlayScrolling( const wxWindow* aWindow, bool overlay )
+{
+    gtk_scrolled_window_set_overlay_scrolling( GTK_SCROLLED_WINDOW( aWindow->GetHandle() ),
+                                               overlay );
+}

libs/kiplatform/include/kiplatform/ui.h

@@ -101,6 +101,21 @@ namespace KIPLATFORM
          * @return System scale factor in use, defaulting to the wxWidgets method
          */
         double GetSystemScaleFactor( const wxWindow* aWindow );
+
+        /**
+         * Tries to determine the size of the viewport of a scrollable widget
+         * (wxDataViewCtrl, wxGrid) that won't be obscured by scrollbars.
+         *
+         * @param aWindow pointer to the scrollable widget to check
+         * @return Viewport size that won't be obscured by scrollbars
+         */
+        wxSize GetUnobscuredSize( const wxWindow* aWindow );
+
+        /**
+         * Used to set overlay/non-overlay scrolling mode in a window.
+         * Implemented only on GTK.
+         */
+        void SetOverlayScrolling( const wxWindow* aWindow, bool overlay );
     }
 }
 

libs/kiplatform/msw/ui.cpp

@@ -120,3 +120,15 @@ double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
 {
     return aWindow->GetContentScaleFactor();
 }
+
+
+wxSize KIPLATFORM::UI::GetUnobscuredSize( const wxWindow* aWindow )
+{
+    return aWindow->GetClientSize();
+}
+
+
+void KIPLATFORM::UI::SetOverlayScrolling( const wxWindow* aWindow, bool overlay )
+{
+    // Not implemented
+}

libs/kiplatform/osx/ui.mm

@@ -119,3 +119,16 @@ double KIPLATFORM::UI::GetSystemScaleFactor( const wxWindow* aWindow )
 {
     return aWindow->GetContentScaleFactor();
 }
+
+
+wxSize KIPLATFORM::UI::GetUnobscuredSize( const wxWindow* aWindow )
+{
+    return wxSize( aWindow->GetSize().GetX() - wxSystemSettings::GetMetric( wxSYS_VSCROLL_X ),
+                   aWindow->GetSize().GetY() - wxSystemSettings::GetMetric( wxSYS_HSCROLL_Y ) );
+}
+
+
+void KIPLATFORM::UI::SetOverlayScrolling( const wxWindow* aWindow, bool overlay )
+{
+    // Not implemented
+}