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Scrollable and drawing panel

I have a big picture and I want the user to load it in a scrollable panel, in other words, the user should load the picture as background of the panel. When loading, the scroll bars should appear. I want to draw in that panel so I have to call myPanel.Invalidate many times. I think if I call myPanel.Invalidate, the panel will be drown from the top so I can't see the bottom of the panel when I want to draw.
May I have a scrollable and drawing panel simultaneously? Is there a solution?
Thanks in advance.

C# panel background image splitting on scrolling

I'm working on a winforms application using C#. I have a form with background image, and a panel on that with transparent background. Some data and controls will be dynamically created on this panel.
This panel has a scroll bar, when I scrolls that background image is splitting and page and data is looking very odd.
Can anyone help me in fixing this issue? All I need that background image should not split on scrolling of the panel...
Thanks in Advance.
Suhasini

This seems to be a limitation on winforms. Check out this post for an explanation.

C# Gray out a control and draw another on it

I´m using WinForms. I want to make a little class, which modifys controls to show it´s working.
I want to draw an overlay over for example a button. It should be a half-transparent gray.
After that i want to draw a ProgressBar on over it (in the center). Similar to This, except using a progress bar.
How can i realize this? I don´t want to set the position of the progressbar, just drawing it on the other one.
How could i do this?
Thanks :)

I have done something similar before.
You need to use Button.DrawToBitmap(Bitmap, Rectangle) to get the image of the button. Then make the Bitmap grayscale (there are multiple algorithms available for this; I have used the last one successfully although probably not originally from this site).
Now, I did this with an entire form instead of a button, but I disabled the form, and then covered the entire form with an image of itself, altered and then covered it with the progress bar (itself in a panel with other controls).
You could just as easily disable the button, cover it with a panel containing the image and the progress bar on top of it.

Creating Overlay Control in winforms

I am using c# winforms to show an Image. The displaying of the image is done using a user control. Now I want to provide the user to draw lines, put other small images, write text etc over the image on an overlay control. How can I provide this functionality? If I use another user control to show the overlay control with transparent back, will that work?? any other solution will be welcome.

You might try approaching this with a canvas (Panel) that handles painting the image as the background and all the annotations/markup afterwards. This will make the foreground appear to be transparent. I expect you'll want to set Control.DoubleBuffer for performance.
You might experiment with setting the style ControlStyles.AllPaintingInWmPaint. Also, try overriding Control.OnPaintBackground and do nothing, and override Control.OnPaint and do all your painting inside there.
If performance is still unacceptable, pay close attention to the PaintEventArgs.ClipRect property. This is the only area you need to paint. The trick is figuring out which of your annotations/overlays intersect with this rectangle and painting them in the correct order.
Either this canvas or a higher level control will need to track mouse movement so you know where to draw the lines, paste images, etc.

c# Winforms: Refreshing a portion of a GUI (containing 1 or more controls)

I have a Control that can overlay multiple C# user controls in my GUI. This control has a semi-transparent background in order to 'grey-out' portions of the GUI and the class looks somethink like this:
public greyOutControl: UserControl
{
// Usual stuff here
protected overide OnPaint()
{
paintBackround();
base.OnPaint();
}
}
Currently the control sometimes gets caught in a loop and constantly re-draws the background, making the semi-transparent color appear less and less transparent.
My idea to combat this is the following (in broad terms):
1) Determine what controls the greyOutControl is on top of
2) call Refresh() on those controls to update the display
3) continue drawing the greyOutControl.
My question is: How can I determine which controls the greyOutControl overlaps?, or is there a way that I can refresh only the part of the GUI that greyOutControl covers?

Why don't you keep track of your transparent controls and paint them after all the other controls are drawn?. Painting anything at the top of the Z-order shouldn't cause the other controls to be repainted.

I don't see a direct way of finding the overlapping controls. I think you might need to check the whole control tree to find out that. About refreshing, you can use Control.Invalidate(Rectangle) method to specify which part to refresh.

The solution to this problem I found was to programmatically take a screen shot of the area being overlayed and then use that image as the background for the control being overlayed. This then allows you to put the alpha overlay into the image within the OnPaint() method and the control to draw itself correctly.
This does have the disadvantage that the background isn't updated in the overlapping control, but unless there was a number of event handlers watching if something changes and then update the overlayed control I cant see any way around the issue. Sometimes I regret not trying to use WPF!