Need help with ScrollWindowEx

[KodeZwerg]

Did you tried to cast to LPARAM() WPARAM() that it work on Windows? At least I do it when I call SendMessage().

[rick2691]

Martin

But then I don't understand why you don't let the memo do the job anyway?

Why do you have it in SynEdit?

I have previously used the SB_THUMBPOSITION method because it is smooth and elegant. The screen just stays where it is upon your exiting the search, instead popping to a new placement.

Rick

[rick2691]

Martin

or retrieves the WM_PAINT message from the application queue.

What is the code that used in SynEdit to do "the latter," as you cited. I would like to give it a try.

Rick

[rick2691]

KodeZwerg

Did you tried to cast to LPARAM() WPARAM() that it work on Windows?

No. It had not needed them. Can you post your code for those operations? I will try them out.

Rick

[Martin_fr]

or retrieves the WM_PAINT message from the application queue.

What is the code that used in SynEdit to do "the latter," as you cited. I would like to give it a try.

SynEdit simply exits from the event handler. Then the message queue is automatically processed by the LCL.

Your code normally runs in an event (OnClicked, OnIdle, On....) and as soon as your code returns (exits the event handler) the LCL continues with the message queue.

And that will include WM_Paint events. Afaik paint events are done with the lowest priority. So if you keep receiving other events, and take long enough to handle them so more can queue up, then paint can be deferred. However usually in that case you want to at least skip a handful paint events, before doing them in one combined sweep.
However if you don't run any data processing loops in your code, then there should be no speed/delay issues.

You can always check in the debugger, by setting breakpoints in the relevant paint events (unless its an OS painted widget, and there is no paint event in the LCL / though even then there should be low level lcl code that can be used to set a breakpoint / richmemo likely has its own Paint method). Make the breakpoint "not breaking" (remove the checkmark in the options of the breakpoint), and then in the breakpoint window you can watch the hitcount.

Or you can use normal breakpoints (actually pause at the breakpoint). So you can see the effect of ScrollWindowEx, and what the paint handler outputs as separate steps.
Of course for that you need to make sure nothing overlaps the richmemo, and it is **always** in view. Not hidden by the IDE, not hidden by any other app.

At least on Windows (tested Win10 64bit scrolling SynEdit): When you set a breakpoint, an step over ScrollWindowEx, the effect is immediate. You can see it happen on the screen. Of course at that time any "scrolled in" content is not yet there, and the old content still visible. The "scrolled in" is handled in the paint event.
(Just test it with a SynEdit, by finding the ScrollWindowEX in SynEdit... / and then also break in the paint method. Note that you can pause at the begin of the paint method, but the effect will only be visible when you run the app again, and it returns to "TWindowProcHelper.SendPaintMessage" in the list of callers / It may be immediate if you switch of double buffering, not tested)

[rick2691]

Marti

SynEdit simply exits from the event handler.

I had already tried it with UpdateWindow removed ... so it just exited the handler. Did not help.

Rick

[Martin_fr]

Code: Pascal  [Select][+][-]

1.        AreaRect:= rect(null,null,null,null);
2.        SetVrtPos:= GetScrollPos(PageMemo.handle,SB_VERT); // integer
3.  
4.        GetVrtOK:= ScrollWindowEx (PageMemo.handle,  // RichMemo application
5.                                   0,  // horizontal element
6.                                   (VrtBarPos - SetVrtPos), // old and new positions
7.                                   @AreaRect,
8.                                   @AreaRect,
9.                                   0,
10.                                   @AreaRect,
11.                                   2); // boolean
12.  

I assume "SetVrtPos" means "currently set/applied". IMHO misleading, maybe name it "CurrentVrtPos". But that is just a personal hint/opinion offtopic to the issue.

Where does "VrtBarPos" (the new pos to which you want to scroll?) come from?

And most important: How to you tell the memo, that it got scrolled to "VrtBarPos".
Because as I mentioned: "ScrollWindowEx" does not tell the memo (100% sure). And neither does "UpdoteWindow".

Have you single stepped the code?
Does something happen on the screen, when you call ScrollWindowEx? (When you step over (F8) it).




Mind, I don't know RichMemo. Maybe it uses child windows, and the content you want to scroll is in an altogether different childwindow, and you are passing the wrong handle?
I must say, that IMHO this is highly UNLIKELY. But when nothing works, consider the unlikely.

[rick2691]

Martin

Here is the code:

Code: Pascal  [Select][+][-]

1. procedure TCmdForm.btnFindExitClick(Sender: TObject);  // was BtnFndEscClick
2. var //PageStat:boolean;
3.     OldSelStart, OldSelLength: integer;
4.     HrzBarPos, VrtBarPos, SetVrtPos, SetHrzPos, TmpPos: integer;
5.     HrzBarFnd, VrtBarFnd, GetVrtOK, GetHrzOK: boolean;
6.     AreaRect: TRect;
7. begin
8.   try
9.   //PageMemo.Lines.BeginUpdate; // suspend screen update
10.     FindPanel.visible:= false;
11.     FindActive:= false;
12.  
13.     OldSelStart:= PageMemo.SelStart;
14.     OldSelLength:= PageMemo.SelLength;
15.  
16.     //TmpPos:= GetScrollPos(PageMemo.handle,SB_VERT);  // for pop-up report
17.  
18.     VrtBarFnd:= Is_ScrollBar_Visible(PageMemo.Handle, SB_VERT); // boolean
19.     HrzBarFnd:= Is_ScrollBar_Visible(PageMemo.Handle, SB_HORZ);
20.  
21.     //  *** SetScrollPos Method *** serves all methods
22.     if VrtBarFnd then VrtBarPos:= GetScrollPos(PageMemo.handle,SB_VERT); // integer
23.     if HrzBarFnd then HrzBarPos:= GetScrollPos(PageMemo.handle,SB_HORZ);
24.  
25.     if VrtBarPos>0 then GetVrtOK:= TRUE else GetVrtOK:= FALSE;
26.     if HrzBarPos>0 then GetHrzOK:= TRUE else GetHrzOK:= FALSE;
27.  
28.     {  // *** ScrollInfo Method ***  // Get_Scroll_Info is identical to GetScrollInfo
29.     if VrtBarFnd then                // being duplicated in order to make it editable
30.        GetVrtOK:= Get_Scroll_Info(PageMemo.Handle, SB_VERT, VrtScrollData) //: Boolean;
31.        else GetVrtOK:= false;
32.  
33.     if HrzBarFnd then
34.        GetHrzOK:= Get_Scroll_Info(PageMemo.Handle, SB_HORZ, HrzScrollData) //: Boolean;
35.        else GetHrzOK:= false;
36.     }
37.  
38.     //PageStat:= PageWideStat.checked; // STORE STAT
39.     FormResize(Self);
40.     if AppSize=CmdForm.Width
41.        then PageWideStat.checked:= true
42.        else PageWideStat.checked:= false;
43.     //PageWideStat.checked:= PageStat; // RESET STAT
44.  
45.     RichMemoHighlightReset(PageMemo);
46.  
47.     PageMemo.SelStart:= OldSelStart;
48.     PageMemo.SelLength:= OldSelLength;   // was := OldSelLength; *or* 0
49.  
50. //=======================================
51.     // *** C Code ScrollWindowEx example ***  // DO NOT ATTEMPT TO ACTIVATE THIS CODE
52.     {
53.     ScrollWindowEx(hwnd, -xDelta, -yDelta, (CONST RECT *) NULL,
54.                   (CONST RECT *) NULL, (HRGN) NULL, (PRECT) NULL,
55.                   SW_INVALIDATE);
56.  
57.     UpdateWindow(hwnd);
58.     }
59. //=======================================
60.     // *** SB_THUMBPOSITION Method ***
61.     (*
62.     if GetVrtOK then
63.        begin
64.        SendMessage(PageMemo.handle, WM_VSCROLL, // vertical
65.                    MakeLong(SB_THUMBPOSITION, VrtBarPos), 0);
66.        VrtBarPos:= SetScrollPos(PageMemo.handle, SB_VERT, VrtBarPos, TRUE); //*GOOD*
67.        end; // else showmessage('VRT-SCROLLBAR FAILED 17');
68.  
69.     if GetHrzOK then
70.        begin
71.        SendMessage(PageMemo.handle, WM_HSCROLL, // horizontal
72.                    MakeLong(SB_THUMBPOSITION, HrzBarPos), 0);
73.        HrzBarPos:= SetScrollPos(PageMemo.handle, SB_HORZ, HrzBarPos, TRUE); //*GOOD*
74.        end; // else showmessage('VRT-SCROLLBAR FAILED 17');
75.  
76.     showmessage('SB_THUMBPOSITION DONE');
77.     *)
78. //=======================================
79.     // *** ScrollWindowEx method ***
80.     //(*
81.     if GetVrtOK then
82.        begin
83.        AreaRect:= rect(0,0,0,0);
84.        SetVrtPos:= GetScrollPos(PageMemo.handle,SB_VERT); // integer
85.  
86.        GetVrtOK:= ScrollWindowEx (PageMemo.handle,  // RichMemo application
87.                                   0,  // horizontal element
88.                                   (VrtBarPos - SetVrtPos), // old and new positions
89.                                   @AreaRect,
90.                                   @AreaRect,
91.                                   0,
92.                                   @AreaRect,
93.                                   SW_INVALIDATE); // boolean
94.  
95.        GetVrtOK:= UpdateWindow(PageMemo.handle); // must execute
96.        end else showmessage('VRT-SCROLLBAR FAILED 17');
97.  
98.        showmessage('ScrollWindowEx DONE');
99.     //*)
100. //======================================
101.    
102.   finally
103.     PageMemo.SelStart:= OldSelStart;
104.     PageMemo.SelLength:= OldSelLength;   // was := OldSelLength; *or* 0
105.     PagePassive:= false;
106.   //PageMemo.Lines.EndUpdate;
107.   end;
108. end;

The GET and SET are equivalent to READ and WRITE as they were applied prior to trying to use ScrollWindowEx.

[Martin_fr]

First of all:

If "VrtBarFnd" will be false, then "VrtBarPos" will not be initialized, and "GetVrtOK" will also not be initialized. So the condition at the end, may be true at random.


I might have missed something, but I assume that between

Code: Pascal  [Select][+][-]

1.  if VrtBarFnd then VrtBarPos:= GetScrollPos(PageMemo.handle,SB_VERT);

Code: Pascal  [Select][+][-]

1. SetVrtPos:= GetScrollPos(PageMemo.handle,SB_VERT);

The Scrollbar will actually change?
Otherwise you always scroll by 0 pixel.

I don't see what changes it. Have you debugged and checked that the 2 values are different?

Also what changes the scrollbar pos, and why does whatever that is not actually do the scrolling?

E.g. if at some point (that I have not spotted), you set the Selection to a different location, and the memo scrolls to that different location (thereby updating the scrollbars), then why would you still need to scroll it, if it already did scroll?
If of course the 2 lines that set the selection to OldSelStart/Length are undoing the scroll, then ... Well then SetVrtPos will be the same as VrtBarFnd, and DY will be 0.
... But then, even if you get SetVrtPos before you undo the scroll (reset the old selection), ScrollWindowEx will not fix the issue. It will move the pixels, but the memo will eventually get a paint event, and jump back to where it was.


In any case:
"@AreaRect" (all 3 occurrences) should be "nil".

Code: Pascal  [Select][+][-]

1.       GetVrtOK:= ScrollWindowEx (PageMemo.handle,  // RichMemo application
2.                                   0,  // horizontal element
3.                                   (VrtBarPos - SetVrtPos), // old and new positions
4.                                   NIL,
5.                                   NIL,
6.                                   0,
7.                                   NIL,
8.                                   SW_INVALIDATE); // boolean

If you hand in a pointer, then Windows will always read the rect at the pointer, and restrict scrolling to the rect given. In your case: zero pixel width, zero pixel height => nothing is scrolled).
If you pass in nil, the entire clientrect will be scrolled.

If you pass in "nil", and the 2 values from above are different (dy <> 0) and you set a breakpoint and step over the "ScrollWindowEx" call then you should see the pixels on the screen move to the new location. (This happens immediately during the call / if on Windows)


Mind, this is trying to make the ScrollWindowEx actually do something (which in order to see it, you may have to watch in the debugger). If that solves whatever needs to be solved is another question....

[rick2691]

Have you debugged and checked that the 2 values are different?

Yes, they are different, and they are absolute pixel counts.

If "VrtBarFnd" will be false, then "VrtBarPos" will not be initialized, and "GetVrtOK" will also not be initialized. So the condition at the end, may be true at random.

Good point. They had been globals, and were initiated elsewhere. Here, they are locals, and placed as such to make sure nothing is interfering with the data ... but I forgot to initiate them. I'll fix that and get back to you.

[rick2691]

This has the initiated variables.

Code: Pascal  [Select][+][-]

1. procedure TCmdForm.btnFindExitClick(Sender: TObject);  // was BtnFndEscClick
2. var //PageStat:boolean;
3.     OldSelStart, OldSelLength: integer;
4.     HrzBarPos, VrtBarPos, SetVrtPos, SetHrzPos, TmpPos: integer;
5.     HrzBarFnd, VrtBarFnd, GetVrtOK, GetHrzOK: boolean;
6.     AreaRect: TRect;
7. begin
8.   try
9.   //PageMemo.Lines.BeginUpdate; // suspend screen update
10.     FindPanel.visible:= false;
11.     FindActive:= false;
12.  
13.     OldSelStart:= PageMemo.SelStart;
14.     OldSelLength:= PageMemo.SelLength;
15.  
16.     VrtBarFnd:= false;
17.     HrzBarFnd:= false;
18.     VrtBarPos:= 0;
19.     HrzBarPos:= 0;
20.     SetVrtPos:= 0;
21.     SetHrzPos:= 0;
22.     GetVrtOK:= false;
23.     GetHrzOK:= false;
24.  
25.     //TmpPos:= 0;
26.     //TmpPos:= GetScrollPos(PageMemo.handle,SB_VERT);  // for pop-up report
27.  
28.     VrtBarFnd:= Is_ScrollBar_Visible(PageMemo.Handle, SB_VERT); // boolean
29.     HrzBarFnd:= Is_ScrollBar_Visible(PageMemo.Handle, SB_HORZ);
30.  
31.     //  *** SetScrollPos Method *** serves all methods
32.     if VrtBarFnd then VrtBarPos:= GetScrollPos(PageMemo.handle,SB_VERT); // integer
33.     if HrzBarFnd then HrzBarPos:= GetScrollPos(PageMemo.handle,SB_HORZ);
34.  
35.     if VrtBarPos>0 then GetVrtOK:= TRUE else GetVrtOK:= FALSE;
36.     if HrzBarPos>0 then GetHrzOK:= TRUE else GetHrzOK:= FALSE;
37.  
38.     {  // *** ScrollInfo Method ***
39.     if VrtBarFnd then
40.        GetVrtOK:= Get_Scroll_Info(PageMemo.Handle, SB_VERT, VrtScrollData) //: Boolean;
41.        else GetVrtOK:= false;
42.  
43.     if HrzBarFnd then
44.        GetHrzOK:= Get_Scroll_Info(PageMemo.Handle, SB_HORZ, HrzScrollData) //: Boolean;
45.        else GetHrzOK:= false;
46.     }
47.  
48.     //PageStat:= PageWideStat.checked; // STORE STAT
49.     FormResize(Self);
50.     if AppSize=CmdForm.Width
51.        then PageWideStat.checked:= true
52.        else PageWideStat.checked:= false;
53.     //PageWideStat.checked:= PageStat; // RESET STAT
54.  
55.     RichMemoHighlightReset(PageMemo);
56.  
57.     PageMemo.SelStart:= OldSelStart;
58.     PageMemo.SelLength:= OldSelLength;   // was := OldSelLength; *or* 0
59.  
60. //=======================================
61.     // *** C Code ScrollWindowEx example ***
62.     {
63.     ScrollWindowEx(hwnd, -xDelta, -yDelta, (CONST RECT *) NULL,
64.                   (CONST RECT *) NULL, (HRGN) NULL, (PRECT) NULL,
65.                   SW_INVALIDATE);
66.  
67.     UpdateWindow(hwnd);
68.     }
69. //=======================================
70.     // *** SB_THUMBPOSITION Method ***
71.     (*
72.     if GetVrtOK then
73.        begin
74.        SendMessage(PageMemo.handle, WM_VSCROLL, // vertical
75.                    MakeLong(SB_THUMBPOSITION, VrtBarPos), 0);
76.        VrtBarPos:= SetScrollPos(PageMemo.handle, SB_VERT, VrtBarPos, TRUE); //*GOOD*
77.        end; // else showmessage('VRT-SCROLLBAR FAILED 17');
78.  
79.     if GetHrzOK then
80.        begin
81.        SendMessage(PageMemo.handle, WM_HSCROLL, // horizontal
82.                    MakeLong(SB_THUMBPOSITION, HrzBarPos), 0);
83.        HrzBarPos:= SetScrollPos(PageMemo.handle, SB_HORZ, HrzBarPos, TRUE); //*GOOD*
84.        end; // else showmessage('VRT-SCROLLBAR FAILED 17');
85.  
86.     showmessage('SB_THUMBPOSITION DONE');
87.     *)
88. //=======================================
89.     // *** ScrollWindowEx method ***
90.     //(*
91.     if GetVrtOK then
92.        begin
93.        AreaRect:= rect(0,0,0,0);
94.        SetVrtPos:= GetScrollPos(PageMemo.handle,SB_VERT); // integer
95.  
96.        GetVrtOK:= ScrollWindowEx (PageMemo.handle,  // RichMemo application
97.                                   0,  // horizontal element
98.                                   (VrtBarPos - SetVrtPos), // old and new positions
99.                                   @AreaRect,
100.                                   @AreaRect,
101.                                   0,
102.                                   @AreaRect,
103.                                   SW_INVALIDATE); // boolean result
104.  
105.        GetVrtOK:= UpdateWindow(PageMemo.handle); // must execute
106.        end else showmessage('VRT-SCROLLBAR FAILED 17');
107.  
108.        showmessage('ScrollWindowEx DONE');
109.     //*)
110. //======================================
111.  
112.   finally
113.     PageMemo.SelStart:= OldSelStart;
114.     PageMemo.SelLength:= OldSelLength;   // was := OldSelLength; *or* 0
115.     PagePassive:= false;
116.   //PageMemo.Lines.EndUpdate;
117.   end;
118. end;
119.  

RichMemo is a container that is placed in the Control Form. Its controls are buttons, menus, pop-ups, and short-cut key strokes. Its only children are the scrollbars and PageTabControl.

I have just made a test run, and it still has the same behaviour.

[Martin_fr]

Did you try to
1) replace "@AreaRect" with "nil"
2) debug with a breakpoint before ScrollWindowEx, and then use "F8" until you stepped over it?

Debug in such a way that the RichMemo is at no time hidden, and you can always see it?

If in that case, at the end of stepping the content in the memo moved, then ScrollWindowEx did work. (It does not solve your issue, but it works as documented / You asked, just to make ScrollWindowEx work....).

[rick2691]

Martin

I might have missed something, but I assume that between

     if VrtBarFnd then VrtBarPos:= GetScrollPos(PageMemo.handle,SB_VERT);

    SetVrtPos:= GetScrollPos(PageMemo.handle,SB_VERT);

The Scrollbar will actually change?
Otherwise you always scroll by 0 pixel.

It does a form resize (FormResize), and clears highlighting (RichMemoHighlightReset) from the document.

FormResize checks to see if you have manually changed the size of the form. If you have, it resizes all the panels, toolbars, and pop-ups so they can seen and accessed when they become active.

I have not been changing the form size.

RichMemoHighlightReset iterates through document and removes any highlighting that the word search would have generated.

Yes, highlighting has been properly removed, and both functions are finished before I have hit the EXIT button that activates this section of code.

Rick

[rick2691]

Martin

1) replace "@AreaRect" with "nil"

We have answered this issue before ... Lazarus will not accept the word "nil" for a Pointer RECT function.

2) debug with a breakpoint before ScrollWindowEx, and then use "F8" until you stepped over it?

No. I have never used the debugger. I have forgotten all of the "machine code" I had ever learned, so I can't read its reports.

I just layout a bunch of showmessage('STAGE 1'); 2, 3, etc. to watch what happens. But I have not done that exhaustively, as you are suggesting. But I can attempt that, and get back to you.

I was typing while you had sent those questions, so I have posted an updated procedure just prior to this post. You should look at it.

Rick

[Martin_fr]

1) replace "@AreaRect" with "nil"

We have answered this issue before ... Lazarus will not accept the word "nil" for a Pointer RECT function.

Code: Pascal  [Select][+][-]

1. uses windows, LCLIntf;
2.  
3. procedure TForm1.FormCreate(Sender: TObject);
4. begin
5.   windows.ScrollWindowEx(Handle, 0, 10, nil, nil, 0, nil, SW_INVALIDATE);
6.   LCLIntf.ScrollWindowEx(Handle, 0, 10, nil, nil, 0, nil, SW_INVALIDATE);
7. end;
8.  

There is a ScrollWindowEx in unit LCLIntf (which has compatible implementation for other Widgedsets; and in unit windows (which goes directly to the win API).

Both of them compile with nil, as given above.

2) debug with a breakpoint before ScrollWindowEx, and then use "F8" until you stepped over it?

No. I have never used the debugger. I have forgotten all of the "machine code" I had ever learned, so I can't read its reports.

I just layout a bunch of showmessage('STAGE 1'); 2, 3, etc. to watch what happens. But I have not done that exhaustively, as you are suggesting. But I can attempt that, and get back to you.

I was typing while you had sent those questions, so I have posted an updated procedure just prior to this post. You should look at it.

The debugger in Lazarus works directly with Pascal code.

Menu: Project > Project Options
- Compilation and linking: set optimization to either "none" or "O1"
- Debugging: Enable "Generate info for debugger" and set the "type of debug info" to "dwarf with sets"

In the source-editor either click (left mouse button) the empty space before the line-number to set a breakpoint (a red dot should appear).
Or use F5 to set the breakpoint while the text cursor is at that line.

Then run with F9.
The debugger should pause at the breakpoint (a green arrow in the breakpoint appears).
Now use F8 (several times), it will go to each line with the arguments, and in between to the line with "ScrollWindowEx".
Eventually it goes to the statement after.
At that time the scrolling should have happened.


While paused you can hover over variables, or use "view > debug windows > ..." for much more info.