My painting code consumes too much memory ( rephrased for better clarity )

Google Drive, perhaps.

Ahhhh! So that's what you've been working on. It certainly looks rather nice when static. :)

Whenever I'm double-buffering, I always take the same approach. That is, to keep a single memDC. I then paint _everything_ to this off-screen hdc. When all drawing has been completed, I then blast this bitmap to the screen with a bitblt.

I recently played with making a custom-control for displaying a text-mode (industrial) LCD panel. In this case, each character consists of 8x5 pixels, with the display holding 20x4 characters.
When drawing directly to screen, one can see the bottom-right corner is clearly painted some 10 or 11ms later than the top-left.

The solution? Use an off-screen drawing surface. Draw the panel background, draw the 'off' pixels, draw the 'on' pixels, bitblt the whole thing in 1 near-instantaneous step.


You can see that only if something has changed will the whole picture be re-drawn. Otherwise, we juts blast the already created image to screen with a bilblt - this will happen if part of the window is obscured and then reshown - such as when a window is dragged in-front of the control. I've some controls that calculate a HSL gradient to implement a colour-picker. Without double-buffering, recalculating and drawing thos pixels was painfully slow. Now, it behaves like a blank dialog or empty window - i.e faaast. :)

Here's the drawing code I'm using for the lcdPanel:

====================================================================

LRESULT CALLBACK cLcdTextPanel::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_PAINT:
if (mNeedsUpdate == true)
{
paintBackgroundBitmap();
mNeedsUpdate = false;
}
OnPaint();
break;

====================================================================
void cLcdTextPanel::OnPaint()
{
HDC hdc;
int i, j;
BITMAP bm;
RECT mRect;
PAINTSTRUCT ps;
HBITMAP hbmOld;
GetClientRect(mHwnd, &mRect);
hdc = BeginPaint(mHwnd, &ps);
hbmOld = (HBITMAP) SelectObject(mHdcMem, mBkBmp);
GetObject(mBkBmp, sizeof(bm), &bm);
BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, mHdcMem, 0, 0, SRCCOPY);
SelectObject(mHdcMem, hbmOld);
EndPaint(mHwnd, &ps);
}
====================================================================





void cLcdTextPanel::paintBackgroundBitmap()
{
HDC hdc; // = GetWindowDC(m_hWnd);
HBITMAP bmOld;
RECT mRect;

GetClientRect(mHwnd, &mRect);

// get the Device Context for our window and create another one so we can draw
// a bitmap that will then be used whenever our window needs repainting.
// This means we only have to do the drawing once. After that, we're simply doing
// a bitblt of our created image - Result: we can handle WM_PAINT messages _much_
// quicker than if we were constantly drawing gradient fills
hdc = GetWindowDC(mHwnd);
if (!mHdcMem)
mHdcMem = CreateCompatibleDC (hdc) ;

// This class currently inherits from a class that loads a bitmap for the background from
// a resource. Lets just delete that bitmap first, before we recreate and draw the bitmap ourselves.
if (!mBkBmp)
{
mBkBmp = CreateCompatibleBitmap (hdc, mRect.right, mRect.bottom) ;
}
bmOld = (HBITMAP)SelectObject (mHdcMem, mBkBmp) ;

// HPEN mPen, oldPen;
// mPen = CreatePen(PS_SOLID, 2, RGB(255,255,255));
//////////////////////
//// All drawing to the bitmap that will be used for our window must happen here
GetClientRect(mHwnd, &mRect);
FillRect(mHdcMem, &mRect, bkBrush);

int index=0,x,y;
for (y=0; y<m_numRows; y++)
{
for (x=0; x<m_numCols; x++)
{
drawChar(x,y, mData[index], m_invertedStates[index]);
index++;
}
}
// EndPaint(mHwnd, &ps);

////
/////////////////////
SelectObject(mHdcMem, bmOld);
ReleaseDC(mHwnd, hdc);
}

You're welcome. Thanks for the interesting problem to consider. :)

Sounds like a good idea. I used to upload zip files to RapidShare, MegaUpload and SaveFile in the past, though these have all sine become defunct or useless.

For code like this, I think perhaps pastebin.com is a fairly good (free) service. Not sure if you can upload the file by picking it from the directory, or if you need to copy/paste in the code/data you'd like to make available.

Look forward to seeing more.

:)