* Increased double buffer on x11 efficiency

* Fixed a bug on listbox that allowed Item 0 to be selected with the mouse
* Fixed a possible bug for TfpgTimer that possibly could allow
  timers to be skipped if timer(s) were destroyed during the callback

2 files changed, 61 insertions, 9 deletions

diff --git a/src/corelib/fpgfx.pas b/src/corelib/fpgfx.pas
index cb6c0092..3125bef2 100644
--- a/src/corelib/fpgfx.pas
+++ b/src/corelib/fpgfx.pas
@@ -369,8 +369,17 @@ var
   ctime: TDateTime;
 begin
   ctime := now;
-  for i := 0 to fpgTimers.Count-1 do
-    TfpgTimer(fpgTimers[i]).CheckAlarm(ctime);
+  i := 0;
+
+  while i <  fpgTimers.Count do
+  begin
+    if fpgTimers[i] = nil then
+      fpgTimers.Delete(i)
+    else begin
+      TfpgTimer(fpgTimers[i]).CheckAlarm(ctime);
+      Inc(i);
+    end;
+  end;
 end;
 
 function fpgClosestTimer(ctime: TDateTime; amaxtime: integer): integer;
@@ -387,7 +396,7 @@ begin
   for i := 0 to fpgTimers.Count-1 do
   begin
     t := TfpgTimer(fpgTimers[i]);
-    if t.Enabled and (t.NextAlarm < dt) then
+    if (t <> nil) and t.Enabled and (t.NextAlarm < dt) then
     begin
       dt := t.NextAlarm;
       tb := True;
@@ -597,7 +606,7 @@ var
 begin
   i := fpgTimers.IndexOf(self);
   if i > -1 then
-    fpgTimers.Delete(i);
+    fpgTimers[i] := nil; // we free the item in fpgCheckTimers
   inherited Destroy;
 end;
 
@@ -751,7 +760,8 @@ begin
   fpgCaret.Free;
   
   for i := fpgTimers.Count-1 downto 0 do
-    TfpgTimer(fpgTimers[i]).Free;
+    if fpgTimers[i] <> nil then
+      TfpgTimer(fpgTimers[i]).Free;
   fpgTimers.Free;
 
   FDefaultFont.Free;
diff --git a/src/corelib/x11/gfx_x11.pas b/src/corelib/x11/gfx_x11.pas
index 7fea5804..e505ed1f 100644
--- a/src/corelib/x11/gfx_x11.pas
+++ b/src/corelib/x11/gfx_x11.pas
@@ -132,6 +132,8 @@ type
   end;
 
 
+  { TfpgCanvasImpl }
+
   TfpgCanvasImpl = class(TfpgCanvasBase)
   private
     FDrawing: boolean;
@@ -147,6 +149,8 @@ type
     FClipRegion: TRegion;
     FPixHeight,
     FPixWidth: Integer;
+    FBufferFreeTimer: TObject;
+    procedure   BufferFreeTimer(Sender: TObject);
     procedure   TryFreePixmap;
   protected
     procedure   DoSetFontRes(fntres: TfpgFontResourceBase); override;
@@ -1688,6 +1692,7 @@ destructor TfpgCanvasImpl.Destroy;
 begin
   if FDrawing then
     DoEndDraw;
+  FreeAndNil(FBufferFreeTimer);
   TryFreePixmap;
   inherited Destroy;
 end;
@@ -1730,13 +1735,41 @@ begin
 
     if buffered then
     begin
-      if (FastDoubleBuffer = False) or (FBufferPixmap = 0) or (w <> FPixWidth) or (h <> FPixHeight) then
+      if (FBufferPixmap = 0)
+      or (FastDoubleBuffer = False)
+      or (FastDoubleBuffer and (w > FPixWidth) or (h > FPixHeight))
+      or ((FastDoubleBuffer = False) and ((w <> FPixWidth) or (h <> FPixHeight)))
+      then
       begin
+        if FastDoubleBuffer and ((w > FPixWidth) or (h > FPixHeight)) then
+        begin
+          FPixHeight := h + 30;
+          FPixWidth  := w + 30;
+        end
+        else begin
+          FPixHeight := h;
+          FPixWidth  := w;
+        end;
         TryFreePixmap;
-        FBufferPixmap := XCreatePixmap(xapplication.display, FDrawWindow.FWinHandle, w, h, xapplication.DisplayDepth);
+        FBufferPixmap := XCreatePixmap(xapplication.display, FDrawWindow.FWinHandle, FPixWidth, FPixHeight, xapplication.DisplayDepth);
+      end;
+      if FastDoubleBuffer then
+      begin
+        // Rapid paint events reuse the double buffer which resests a delay
+        // After the delay the double buffer is freed, letting the OS use video
+        // memory if needed.
+        // Things like scrolling and resizing are fast
+
+        // Reset the timers next trigger
+        if FBufferFreeTimer = nil then
+        begin
+          FBufferFreeTimer := TfpgTimer.Create(500);
+          TfpgTimer(FBufferFreeTimer).OnTimer := @BufferFreeTimer;
+        end
+        else
+          TfpgTimer(FBufferFreeTimer).Enabled := False;
+        TfpgTimer(FBufferFreeTimer).Enabled := True;
       end;
-      FPixHeight := h;
-      FPixWidth := w;
       FDrawHandle   := FBufferPixmap;
     end
     else
@@ -1836,6 +1869,15 @@ begin
       Trunc(64 * a1), Trunc(64 * a2));
 end;
 
+procedure TfpgCanvasImpl.BufferFreeTimer(Sender: TObject);
+begin
+  {$IFDEF DEBUG}
+  WriteLn('fpGFX/X11: Freeing Buffer w=', FPixWidth, ' h=', FPixHeight);
+  {$ENDIF}
+  TryFreePixmap;
+  FreeAndNil(FBufferFreeTimer);
+end;
+
 procedure TfpgCanvasImpl.TryFreePixmap;
 begin
   if FBufferPixmap > 0 then