I'm new to win32 and there are some concepts I haven't fully grasped. For one, the difference between HDC and HWND. I understand (or think I understand) that they're handles to a objects and that hdc's can be derived from hwnd's. Like in the case of BeginPaint:
hdc = BeginPaint(hWnd, &ps);
But i don't fully understand what seperates each as certain methods have hdc as parameters and some use hwnd
Secondly, I'm not sure what SelectObject and GetObject do. I think that they associate handles with various objects, like in the case of this bitmap drawing function:
BOOL DrawBitmap (HDC hDC, INT x, INT y, INT width, INT height, HBITMAP hBitmap,
DWORD dwROP)
{
HDC hDCBits;
BITMAP Bitmap;
BOOL bResult;
hDCBits = CreateCompatibleDC(hDC);
GetObject(hBitmap, sizeof(BITMAP), (LPSTR)&Bitmap);
SelectObject(hDCBits, hBitmap);
bResult = StretchBlt(hDC, x, y, width, height,hDCBits, 0, 0, Bitmap.bmWidth,
Bitmap.bmHeight, dwROP);
DeleteDC(hDCBits);
return bResult;
}
But despite all of this I don't understand exactly what they do or how they work. Thanks, in advance.
Related
I am getting a very poor peformance drawing with Win32. It takes too much time and needs improving. Please advise.
Here is what I do.
HDC dc = GetDC(wnd);
HDC memoryDc = CreateCompatibleDC(dc);
HBITMAP memoryMapBitmap = CreateCompatibleBitmap(dc, 400, 400);
HGDIOBJ originalBitmap = SelectObject(memoryDc, memoryMapBitmap);
Then, I draw in a for-loop as follows.
HBRUSH brush = (HBRUSH)GetStockObject(DC_BRUSH);
SetDCBrushColor(memoryDc, colorRef);
FillRect(memoryDc, &rect, brush);
And finally, I do a cleanup
SelectObject(memoryDc, originalBitmap);
DeleteDC(memoryDc);
ReleaseDC(wnd, dc);
Drawing takes a lot of time (several seconds). Is there a way to draw faster with Win32?
Thanks in advance!
It looks like I have solved it. Below is the solution with some comments.
I have a dialog defined in RC-file. There is a control to display a bitmap image in the dialog.
CONTROL "", IDC_MEMORY_MAP, WC_STATIC, SS_BITMAP | SS_CENTERIMAGE | SS_SUNKEN, 9, 21, 271, 338, WS_EX_LEFT
In the run-time I need to create, draw and display a bitmap:
HWND map = GetDlgItem(dlg, IDC_MEMORY_MAP);
HBITMAP bitmap = createMemoryMapBitmap(map);
bitmap = (HBITMAP)SendMessage(map, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)bitmap);
DeleteObject(bitmap); // (!) this is a very important line, otherwise old bitmap leaks
Code that finds out the size of the bitmap to create:
HBITMAP createMemoryMapBitmap(HWND map) {
RECT rect = {0, 0, 0, 0};
GetClientRect(map, &rect);
SIZE size = {rect.right - rect.left, rect.bottom - rect.top};
HDC dc = GetDC(map);
HBITMAP bitmap = doCreateMemoryMapBitmap(dc, &size);
ReleaseDC(map, dc);
return bitmap;
}
Finally, we actually create the bitmap and draw on it:
HBITMAP doCreateMemoryMapBitmap(HDC dc, LPSIZE bitmapSize) {
// create 24bpp bitmap in memory in order to draw fast
BITMAPINFO info;
memset(&info, 0, sizeof(info));
info.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
info.bmiHeader.biWidth = bitmapSize->cx;
info.bmiHeader.biHeight = bitmapSize->cy;
info.bmiHeader.biPlanes = 1;
info.bmiHeader.biBitCount = 24;
info.bmiHeader.biCompression = BI_RGB;
void *pixels = NULL;
HBITMAP memoryBitmap = CreateDIBSection(dc, &info, DIB_RGB_COLORS, &pixels, NULL, 0);
HDC memoryDc = CreateCompatibleDC(dc); // (!) memoryDc is attached to current thread
HGDIOBJ originalDcBitmap = SelectObject(memoryDc, memoryBitmap);
// drawing code here
// perform windows gdi cleanup
SelectObject(memoryDc, originalDcBitmap); // restore original bitmap in memoryDC (optional step)
DeleteDC(memoryDc); // this releases memoryBitmap from memoryDC
return memoryBitmap;
}
The idea above is to create a 24bpp bitmap in the memory and draw on it. This way drawing is fast, as #IInspectable pointed out.
If display is in the indexed color mode, e.g. 16 or 256 colors, it seems Windows native control is smart enough to convert the color depth automatically displaying the bitmap.
There is an HBITMAP which can be displayed successfully. I want get a portion (specified by a rect) of the bitmap, so is the following code but the returned bitmap is always black. Is there something wrong with the code? Thanks.
HBITMAP GetSelectedBitmap(HBITMAP p_bitmap, int x, int y, int width, int height){
HDC l_srcDc = ::CreateCompatibleDC(NULL);
::SelectObject(l_srcDc, p_bitmap);
HDC l_dstDc = ::CreateCompatibleDC(l_srcDc);
HBITMAP l_newBitmap = CreateCompatibleBitmap(l_dstDc, width, height);
HBITMAP l_oldBitmap = (HBITMAP)::SelectObject(l_dstDc, l_newBitmap);
ASSERT(0 != ::BitBlt(l_dstDc, 0, 0, width, height, l_srcDc, x, y, SRCCOPY));
HBITMAP l_clippedBitmap = (HBITMAP)::SelectObject(l_dstDc, l_oldBitmap);
::DeleteDC(l_srcDc);
::DeleteDC(l_dstDc);
return l_clippedBitmap;}
I found the cause, change
HBITMAP l_newBitmap = CreateCompatibleBitmap(l_dstDc, width, height);
to
HBITMAP l_newBitmap = CreateCompatibleBitmap(l_srcDc, width, height);
fix the issue. that means CreateCompatibleBitmap should use the source DC.
I tried to convert from unsigned char array to Bitmap in MFC as follow.
BITMAPFILEHEADER* bmfh;
bmfh = (BITMAPFILEHEADER*)rgbByte;
BITMAPINFOHEADER* bmih;
bmih = (BITMAPINFOHEADER*)(rgbByte + sizeof(BITMAPFILEHEADER));
BITMAPINFO* bmi;
bmi = (BITMAPINFO*)bmih;
void* bits;
bits = (void*)(rgbByte + bmfh->bfOffBits);
HDC hdc = ::GetDC(NULL);
HBITMAP hbmp = CreateDIBitmap(hdc, bmih, CBM_INIT, bits, bmi, DIB_RGB_COLORS) ;
rgbByte is my unsigned char array and the problem is hbmp is always unused and never get data. What is the problem?
Thanks
HDC hdc = ::GetDC(NULL);
gets the DC of the entire screen. I doubt that is what you want. More likely you have a window or image control into which you want to place the bitmap. You need to get the DC of that window instead by passing to GetDC() it's m_hWnd member.
I'm trying to capture several software window and print them to my software. The goal is to be able to view two different software side to side even if they overlap.
void MyWindowFinder::drawTo(HWND hWnd){
MyWindow* currentWindow = anchorWindow;
HDC hdcRendering;
HDC hdcMemRendering;
PAINTSTRUCT ps;
hdcRendering = BeginPaint(hWnd, &ps);
hdcMemRendering = CreateCompatibleDC(hdcRendering);
int widthToRender = 0;
for(int i = 0; i < this->anchorWindow->winID ; i++){
HDC hdcCapture;
HDC hdcMemCapture;
HBITMAP hBitmap;
HGDIOBJ oldCaptureBitmap;
HGDIOBJ oldRenderingBitmap;
RECT clientRect;
GetClientRect(currentWindow->hwnd,&clientRect);
int width = clientRect.right-clientRect.left;
int height = clientRect.bottom-clientRect.top ;
if (!(hdcCapture = GetDC (currentWindow->hwnd))){
return;
}
hdcMemCapture = CreateCompatibleDC(hdcCapture);
hBitmap = CreateCompatibleBitmap(hdcCapture,clientRect.right-clientRect.left,clientRect.bottom-clientRect.top);
oldCaptureBitmap = SelectObject(hdcMemCapture, hBitmap);
BitBlt(hdcMemCapture, 0, 0, width, height, hdcCapture, 0,0, SRCCOPY|CAPTUREBLT);
oldRenderingBitmap = SelectObject(hdcMemRendering, hBitmap);
BitBlt(hdcRendering, widthToRender, 0, width, height, hdcMemCapture, 0, 0, SRCCOPY);
widthToRender+= width;
SelectObject(hdcMemRendering, oldRenderingBitmap);
SelectObject(hdcMemCapture, oldCaptureBitmap);
DeleteDC(hdcMemCapture);
DeleteDC(hdcCapture);
DeleteObject(hBitmap);
currentWindow = currentWindow->previousWindow;
}
DeleteDC(hdcMemRendering);
DeleteDC(hdcRendering);
EndPaint(hWnd, &ps);
}
This works pretty well and I can print two overlapping window side to side in my software :
However I'm facing a tricky problem. When I click on any element of one of my children software, they are not drawn in my software.
Do you have any idea why, and how I could solve this problem ?
I want to know how to write text on a particular window starting at a given location in the window using the Windows API.
For example if the coordinates within the window where the text is to be written are (x,y) = (40,10) then what do I need to do to write a line of text to a particular window at that location in the window?
Suppose your window name is "hwnd" and the text which u want to write on that window at x,y coordinate is say stored in "message" where
LPCWSTR message=L"My First Window"; then
RECT rect;
HDC wdc = GetWindowDC(hwnd);
GetClientRect (bgHandle, &rect) ;
SetTextColor(wdc, 0x00000000);
SetBkMode(wdc,TRANSPARENT);
rect.left=40;
rect.top=10;
DrawText( wdc, message, -1, &rect, DT_SINGLELINE | DT_NOCLIP ) ;
DeleteDC(wdc);
Thats it.. remember this is just one example.
I am hoping this a more complete answer...
void OnPaint(HWND hWnd)
{
RECT rect;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
GetClientRect(hWnd, &rect);
SetTextColor(hdc, RGB(0xFF, 0x00, 0x00));
SetBkMode(hdc, TRANSPARENT);
rect.left = 40;
rect.top = 10;
DrawText(hdc, L"Hello World!", -1, &rect, DT_SINGLELINE | DT_NOCLIP);
SelectObject(hdc, oldPen);
DeleteObject(hPen);
EndPaint(hWnd, &ps);
}
This would then be called from the WM_PAINT message in the WndProc.