From 7e24823c22b645c795b71d064a738f90605d925c Mon Sep 17 00:00:00 2001
From: zeljko <zeljko@lazarus-ide.org>
Date: Wed, 24 Mar 2010 11:16:24 +0000
Subject: [PATCH] Gtk2: scrollbar - fixed pagesize calculation, fixes #16001

git-svn-id: trunk@24188 -
---
 lcl/interfaces/gtk2/gtk2wscontrols.pp | 32 ++------------------
 lcl/interfaces/gtk2/gtk2wsstdctrls.pp | 42 ++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 40 deletions(-)

diff --git a/lcl/interfaces/gtk2/gtk2wscontrols.pp b/lcl/interfaces/gtk2/gtk2wscontrols.pp
index e76c66926d..c8cd721b2e 100644
--- a/lcl/interfaces/gtk2/gtk2wscontrols.pp
+++ b/lcl/interfaces/gtk2/gtk2wscontrols.pp
@@ -122,33 +122,17 @@ function Gtk2RangeScrollCB(ARange: PGtkRange; AScrollType: TGtkScrollType;
 var
   Msg: TLMVScroll;
   MaxValue: gdouble;
-  ScrolledBeyondMaximum: Boolean;
 begin
   Result := CallBackDefaultReturn;
 
-  ScrolledBeyondMaximum:=false;
-  if (ARange^.adjustment<>nil) then begin
-    MaxValue:=ARange^.adjustment^.upper-Max(ARange^.adjustment^.page_size-1,0);
-    //debugln(['Gtk2RangeScrollCB AValue=',AValue,' MaxValue=',MaxValue]);
-    if AValue>MaxValue then begin
-      // limit to maximum
-      ScrolledBeyondMaximum:=true;
-      AValue:=MaxValue;
-      if AValue=ARange^.adjustment^.value then begin
-        // already at maximum
-        Result:=not Result;
-        exit;
-      end;
-    end;
-  end;
-
   //Assert(False, Format('Trace:[Gtk2RangeScrollCB] Value: %d', [RoundToInt(AValue)]));
   if G_OBJECT_TYPE(ARange) = gtk_hscrollbar_get_type then
     Msg.Msg := LM_HSCROLL
   else
     Msg.Msg := LM_VSCROLL;
 
-  with Msg do begin
+  with Msg do
+  begin
     Pos := Round(AValue);
     if Pos < High(SmallPos) then
       SmallPos := Pos
@@ -159,18 +143,6 @@ begin
     ScrollCode := GtkScrollTypeToScrollCode(AScrollType);
   end;
   Result := DeliverMessage(AWidgetInfo^.LCLObject, Msg) <> 0;
-
-  if (Result=CallBackDefaultReturn) and ScrolledBeyondMaximum
-  and (ARange^.adjustment<>nil) then begin
-    // scroll to maximum
-    // otherwise when dragging fast with the mouse the bar will not reach the maximum
-    MaxValue:=ARange^.adjustment^.upper-Max(ARange^.adjustment^.page_size-1,0);
-    if ARange^.adjustment^.value<>MaxValue then begin
-      ARange^.adjustment^.value:=MaxValue;
-      gtk_adjustment_changed(ARange^.adjustment);
-    end;
-    Result:=not Result;
-  end;
 end;
 
 function Gtk2ScrolledWindowScrollCB(AScrollWindow: PGtkScrolledWindow; AEvent: PGdkEventScroll; AWidgetInfo: PWidgetInfo): gboolean; cdecl;
diff --git a/lcl/interfaces/gtk2/gtk2wsstdctrls.pp b/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
index 75d0bda981..d9b515a99d 100644
--- a/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
+++ b/lcl/interfaces/gtk2/gtk2wsstdctrls.pp
@@ -74,6 +74,7 @@ type
   published
     class function  CreateHandle(const AWinControl: TWinControl; const AParams: TCreateParams): TLCLIntfHandle; override;
     class procedure SetParams(const AScrollBar: TCustomScrollBar); override;
+    class procedure ShowHide(const AWinControl: TWinControl); override;
   end;
 
   { TGtk2WSCustomGroupBox }
@@ -2112,11 +2113,13 @@ var
 begin
   with TScrollBar(AWinControl) do
   begin
-{    Adjustment := GTK_ADJPgtkAdjustment(
-                   gtk_adjustment_new(1, Min, Max, SmallChange, LargeChange,
-                     Pagesize));
+    {We use Max + PageSize because the GTK scrollbar is meant to scroll from
+     min to max-pagesize which would be different from the behaviour on other
+     widgetsets.}
+    Adjustment := PGtkAdjustment(gtk_adjustment_new(Position, Min,
+      Max + PageSize, SmallChange, LargeChange, PageSize));
 
- }   if (Kind = sbHorizontal) then
+    if (Kind = sbHorizontal) then
       Widget := gtk_hscrollbar_new(Adjustment)
     else
       Widget := gtk_vscrollbar_new(Adjustment);
@@ -2135,12 +2138,31 @@ class procedure TGtk2WSScrollBar.SetParams(const AScrollBar: TCustomScrollBar);
 var
   Range: PGtkRange;
 begin
-  Range := GTK_RANGE(Pointer(AScrollBar.Handle));
-  //set properties for the range
-  // Note: gtk only allows: Min < Max
-  gtk_range_set_range     (Range, AScrollBar.Min, Max(AScrollBar.Min+1,AScrollBar.Max));
-  gtk_range_set_increments(Range, AScrollBar.SmallChange, AScrollBar.LargeChange);
-  gtk_range_set_value     (Range, AScrollBar.Position);
+  with AScrollBar do
+  begin
+    Range := GTK_RANGE(Pointer(Handle));
+    {for gtk >= 2.14 use gtk_adjustment_configure}
+    with Range^.adjustment^ do
+    begin
+      value := Position;
+      lower := Min;
+      upper := Max + PageSize;
+      step_increment := SmallChange;
+      page_increment := LargeChange;
+      page_size := PageSize;
+    end;
+    gtk_adjustment_changed(Range^.adjustment);
+  end;
+end;
+
+class procedure TGtk2WSScrollBar.ShowHide(const AWinControl: TWinControl);
+begin
+  if not AWinControl.HandleAllocated then
+    exit;
+  if AWinControl.HandleObjectShouldBeVisible then
+    SetParams(TCustomScrollBar(AWinControl));
+  Gtk2WidgetSet.SetVisible(AWinControl,
+    AWinControl.HandleObjectShouldBeVisible);
 end;
 
 end.