I've been developing an app for a while now that has a textbox with a vertical scrollbar. It's worked perfectly up until today. Today, after making some changes unrelated to scrolling, I noticed that the scrollbar wasn't moving up and down when I drag it with the mouse. The textbox that owns the scrollbar scrolls just fine, but the scrollbar doesn't move till I release the mouse button!
This is extremely annoying, and confusing for users of my application. My question is this: what would cause such a thing to happen, and how can I fix it?
The cause of the scrollbar not moving was my use of this overridden property:
protected override CreateParams CreateParams
{
get
{ // Turn on WS_EX_COMPOSITED
CreateParams cp = base.CreateParams; cp.ExStyle |= 0x02000000;
return cp;
}
}
I was using it to ensure double-buffering on all controls, but it had unintended side effects.
Related
so I'm challenging myself by making a game-engine using GDI.
So far I've managed to make made a few games using GDI - however I have recent hit a problem I'd like some help with.
I have implemented a UI system and have found out that the GDI Translate function moves the entire canvas. Subsequently all my mouse coordinates are offset causing my UI system to not work as expected.
Question: Is there any way to make a Panel transparent on the Paint method?
I have tried to set the clear colour to transparent but that only makes the panel black.
I cannot point to a source for this, but I did some testing now and my explanation is as following:
When I set the BackgroundColor of the panel to Colors.FromArgb(50,0,0,0) then this worked, because whenever I changed the Backgroundcolor of the Form the panel lives on, then the color of the form shined through the panel.
But: the other controls that lived behind this panel have not been visible all the time. I am sure that for performance reasons the rendering of the controls only happens if they are visible to the user, that means they are not coverd by an other control. So the color of the form is shining through because the transparent color actually works, but the controls behind the panel are not rendered because they are covered by an other control.
You have to write your own control:
public class TransparentPanel : Panel
{
protected override CreateParams CreateParams
{
get
{
var cp = base.CreateParams;
cp.ExStyle |= 0x00000020; //WS_EX_TRANSPARENT
return cp;
}
}
}
this tells windows, that the control is transparent and the controls that are are in z-order behind this control have to be rendered, too.
I have an application in which I can move from 1 user control to many user controls. When I was moving to many controls, I was getting flickering issues.
To solve the flickering I enabled Double Buffering via -
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
return cp;
}
}
It indeed solved the issue of flickering. But introduced a new problem, In which sometimes my user control isn't painted completely. A black window is appeared. To solve this, I need to minimize and maximize the software and it appears properly.
What I think is that, while double buffering is painting all the user
controls at one shot, One or more user control is still generating its
controls. And at the time of master painting, that control was not
ready.
Here is the image for getting proper idea -
As shown in image, There is one form, containing 4 user controls in this particular scenario. Each user control further, contains other controls/user controls.
What is probably going wrong in this issue?
I solved this by changing TrasnsparencyKey in form design from black to another color but not black, try one color that you are not using.
I am using a library in which enables me to animate movement of WinForm elements (linked below), when I use it to move a transparent panel across the form (which has a picture background) there is an extraordinary amount of tearing.
I believe the fix is to get winforms to refresh at a rate of 30fps without being laggy. I tried settings a timer to do This.Refresh(); at 30 times a second but it just ended up with slow loading. So how would I achieve a nice refresh rate of the form?
The link described above is here -> http://code.google.com/p/dot-net-transitions/wiki/CodingWithTransitions#Creating_a_transition_that_works_on_a_single_property
Here is an example of the tearing. It might have something to do with the fact that the panel's backcolor is set to "transparent"
http://screencast.com/t/XIr3NkGI
I used this ages ago when I had trouble with controls on a form flickering, in my case there were many controls and when loading the form the controls would flicker quite badly.
In the end I used this:
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000;
return cp;
}
}
Paste that in your form.
It activates double buffering at the form level and for all controls within it.
HOWEVER, while it stopped my flickering issue it greatly reduced the speed at which the forms elements seemed to move as they don't get drawn until they are 100% ready.
I guess you can try and see if it suits your situation.
I added this to my form's constructor code:
this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.DoubleBuffer, true);
But it still shows ugly artifacts when it loads the controls, whenever they change (the form and its components change (need updating) often).
What do I need to do differently?
This only has an effect on the form itself, not the child controls. If you have a lot of them then the time they need to take turns painting themselves becomes noticeable, it leaves a rectangular hole where the control goes that doesn't get filled up until the child control gets it turn.
What you'd need to combat this is double-buffering the entire form and the controls. That's an option available since Windows XP which made the WS_EX_COMPOSITED style flag available. Paste this into your form to turn it on:
protected override CreateParams CreateParams {
get {
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
return cp;
}
}
It doesn't speed up the painting at all, but the form snaps onto the screen after a delay. Eliminating the visible paint artifacts. Really fixing the delay requires not using controls. Which you'd do by using the OnPaint method to draw the 'controls' and making the OnMouseClick event smart about what 'control' got clicked by the user.
Tried the CreateParams override as suggested here, however, the taskbar button does not appear on initial load. The user has to activate another window, then re-activate the target window before the taskbar button appears.
Any reason why this is so? How do you workaround this?
Try adding the WS_EX_APPWINDOW flag to the ExStyle property of CreateParams.
Windows is trying to guess whether your window should have a taskbar button by looking at the caption and other styles. The WS_EX_APPWINDOW makes it explict so Windows doesn't have to guess.
WS_EX_TOOLWINDOW makes it explicit that you should NOT have a taskbar button.
Edit: like this
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x0040000; // add WS_EX_APPWINDOW
cp.Style &= ~0x00C00000; // remove WS_CAPTION
return cp;
}
}