Why painting FlowLayoutPanel with complex user controls childs takes ages?

Question

I'm using "FlowLayoutPanel" to store a complex GUI. This structure contains two types of UserControls:

"S" Simple U.C (Constant Size)
"C" Another FlowLayoutPanel that can have those to type as childs.. and so on.

When I have this kind of structure:

1.C

S
S
C :

1.s

2.C
```
   1.S
   2.S
```

It takes about 15 sec to render this control, Every time this control visble changes the GUI get stuck for 15+- sec until its render the whole components.

*Note 1: the complex "C" control is auto sized which contains the FlowLayoutPanel. all "inner" "C" components get their height changed when adding childs. the main\master "C" control got a fix size and have scroll bar.

*Note 2: I extended the FlowLayoutPanel to have some double buffered optimizations:

public sealed class FlowLayoutPanelEx : FlowLayoutPanel {

    public FlowLayoutPanelEx()
        : base()
    {
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
    }

    protected override void OnScroll(ScrollEventArgs se)
    {
        this.Invalidate();

        base.OnScroll(se);
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x02000000; // WS_CLIPCHILDREN
            return cp;
        }
    }

}

5 Simple, and 3 Complex. 8 Totals. Exactly in the order I wrote in the question. — Aviram Fireberger, Jul 14 '16 at 10:59
Rendering 8 controls does __not__ take 15 seconds. The time must go somewhere else. Why do you do an Invalidate in the scroll? Seems rather weird to me.. — TaW, Jul 14 '16 at 11:10
I used the profiler to snap before and stop it once it was shown. It showed me the "set_Visible" took 87.3% of the time Found it on: http://stackoverflow.com/questions/3341032/during-flowlayoutpanel-scrolling-background-distorts-flickers — Aviram Fireberger, Jul 14 '16 at 11:21
No.. they have normal settings, except the auto size which is different from the default (it's True) — Aviram Fireberger, Jul 14 '16 at 12:36
I just tried to put 15 Simple UC to a panel with space.. this doesn't get flicker or time to render,, when I'm using "FlowLayoutPanel" instead of a normal "Panel" I get this bug, — Aviram Fireberger, Jul 14 '16 at 12:37
I just don't want to handle the auto size + adding\removing changing controls size and height by myself in the panel instead of using the flowlayout which does the work for me... — Aviram Fireberger, Jul 14 '16 at 12:38
I meant what are you __drawing__? Do you really __draw__ them, or are they just there and the system renders them. You have set styles that imply owner-drawing, yes? — TaW, Jul 14 '16 at 15:29
they are just there, and the system render them. I didnt override the paint function — Aviram Fireberger, Jul 15 '16 at 17:03

score 0 · Accepted Answer · answered Aug 03 '16 at 09:10

Solved by overriding the "SuspendLayout" and "ResumeLayout" functions,

When I need to paint this control and nothing changed, I call the SuspendLayout function which calls the "SuspendLayout" function for each child recursivly.

After the paint is over. I call the "ResumeLayout" which does the same.

This will make the user control not to "RePaint" and calculate all the childs\parent size, and just paint the control at the same state he was before.

Reduce the rendering time from 15 Sec to 0.2 Sec :)

Why painting FlowLayoutPanel with complex user controls childs takes ages?

1 Answers1