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VB Forum / COM / June 2008how to pass a drawing area limitation?
I'm writing a grid control which does the main work to draw the grid lines into a picturebox and handles cursor movement, scrolling, and so on. The cell content itself should be drawn by the calling application, so I am looking for a fast way to pass something like a viewport of the picturebox in a control_cellpaint event. If I pass the picturebox itself the app can overwrite the whole picturebox, if I pass a separate bitmap and copy this one back into the grid's bitmap this would probably take too much time if a full screen grid with hundreds of cells has to be repainted. Is there another way to pass a drawing destination like a picturebox and a rectangle where the host app is limited to draw in? > I'm writing a grid control which does the main work to draw > the grid lines into a picturebox and handles cursor [quoted text clipped - 11 lines] > picturebox and a rectangle where the host app is limited to > draw in? Why not pass the hDC of the PictureBox? To avoid possible Overdrawing of already painted areas, you could wrap your Event with these Calls: IntersectClipRect PicBox.hDC, ..., ... RaiseEvent OwnerDrawnCell PicBox.hDC, x, y, dx, dy SelectClipRgn PicBox.hdc, 0 Olaf > Why not pass the hDC of the PictureBox? > To avoid possible Overdrawing of already painted [quoted text clipped - 3 lines] > RaiseEvent OwnerDrawnCell PicBox.hDC, x, y, dx, dy > SelectClipRgn PicBox.hdc, 0 I'm not familiar with these two API calls, but if IntersectClipRect defines a rectangle where the next drawings are limited to take place (and SelectClipRgn sets it back to the complete PicBox area), why should the region described once more in the event parameters? I want exactly to avoid this, else I could simply pass the PicBox itself with x,y,dx,dy and trust that the calling app would be so kind to draw only inside the rectangle. Try the links in: www.vb32.com >> Why not pass the hDC of the PictureBox? >> To avoid possible Overdrawing of already painted [quoted text clipped - 11 lines] > trust that the calling app would be so kind to draw only inside the > rectangle. > > Why not pass the hDC of the PictureBox? > > To avoid possible Overdrawing of already painted [quoted text clipped - 12 lines] > with x,y,dx,dy and trust that the calling app would be so > kind to draw only inside the rectangle. Hmm, maybe you are after SetViewPortOrg then, if you want to let the client-app draw with relative cell-coords. But setting such an overdraw-limitation, (which clips any drawn user-content to the current cell) is not a bad "protection"-idea - since the user could use *any* GDI-Call, even if the call itself does *not* support separate clipping-rects in its params as e.g. ExtTextOut. Your choice. Olaf |
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