I am using plain winapi c to create a GUI, I am new to this language and am struggling with something many might think is basic. Could someone please explain to me how I change the background colour for static text because currently is transparent. The code I am using for the text is:
hwndStatic = CreateWindow(TEXT("static"), TEXT(""),
WS_CHILD | WS_VISIBLE,
10, 70, 90, 25, hwnd, NULL, g_hinst, NULL);
In general, you change the drawing of static text controls by handling WM_GETCTLCOLORSTATIC.
In that handler, you can change things about the DC, like the text color, background mode, background color, even the font that's selected.
You can also return a handle to a GDI brush (using a cast to get it by the type system). The control will erase itself first with the brush and then draw the text.
The callback will happen for all static controls that are children of the current window, so you first test to see if it's the child you care about.
For example:
case WM_CTLCOLORSTATIC:
HWND hwnd = (HWND) lParam;
if (hwnd == hwndStatic) {
HDC hdc = (HDC) wParam;
::SetTextColor(hdc, RGB(0xFF, 0, 0)); // set the text to red
::SetBkMode(hdc, OPAQUE);
::SetBkColor(hdc, RGB(0x00, 0xFF, 0x00)); // set background to green
HBRUSH hbrBackground = ::GetSysColorBrush(COLOR_WINDOW);
return (INT_PTR) hbrBackground;
}
return 0;
This shows several things you can do. You probably don't want to do all of them, but it can be educational to see them all in action.
Note that if you create a brush to return, you have to keep track of it and delete it later. I've avoided this issue by relying on GetSysColorBrush. The system owns those, so you shouldn't delete them. You can also use GetStockObject for system GDI objects that you don't have to manage. But if you need a custom color, you'll have to use CreateSolidBrush and then clean it up.
Respond to the WM_CTLCOLORSTATIC message in your program and have it return a brush object of the proper color.
I've slightly modified the example from the link:
case WM_CTLCOLORSTATIC:
{
HWND hWnd = (HWND) lParam;
if (hWnd == hMyStatic)
{
HBRUSH hbrBkgnd = CreateSolidBrush(RGB(0,0,0));
return (INT_PTR)hbrBkgnd;
}
return 0;
}
Related
I don't get how I am supposed to handle brushes for coloring static text background.
At first everything looks nice as it is supposed to be:
However, after the statics have been redrawn for several times, they change to this:
I also noticed this depends on whether I'm straight returning the same brush in every case (for debugging) or using the actual code with different cases(grey boxes after first redrawing).
My WM_CTLCOLORSTATIC message handling looks like this:
case WM_CTLCOLORSTATIC:
{
HDC hdcStatic = (HDC) wParam;
SetTextColor(hdcStatic, RGB(0,0,0));
HBRUSH hbrDefault = CreateSolidBrush(RGB(255,255,255));
return (INT_PTR)hbrDefault;
(Simplified for debugging)
I guess this has something to do with freeing the brushes after using with DeleteObject(), but how could I do this when I need to return the brushes, but I want to delete them before leaving the function?
MSDN resources didn't help: WM_CTLCOLORSTATIC
EDIT : I found my mistake.
I declared my brushes as global variables like this:
HBRUSH hbrBkFoodCat[FOODCAT_LENGTH];
HBRUSH hbrDefault;
But then I initialised them on startup like this:
for(int i=0;i<FOODCAT_LENGTH;i++) {
hbrBkFoodCat[i] = CreateSolidBrush(foodCatClr[i]);
}
HBRUSH hbrDefault = CreateSolidBrush(RGB(255,255,255));
As you can see, I accidentally declared hbrDefault again but this time as a local variable, so at message handling I got that grey boxes (NULL brush).
What I tried out (stupid idea I know), was to initialize them at message handling. Since I just copy-pasted that initialization right into the handling, it became a local variable again, but this time it was 'in range' for the return. This lead me to the assumption something was wrong with freeing the brushes, because of having to redraw it numerous times before getting that grey background (still don't get this though).
Thank you all for your help anyway!
The MSDN documentation for that message says that you MUST free the brush. But you don't have to create/free it everytime. Just create it once and reuse. Free it when you don't need it anymore, but not in the message handler.
Do not create a new brush every time you process a WM_CTLCOLORSTATIC message. That is a resource leak. Create the brush one time, either when you first create the static text control, or when it sends you WM_CTLCOLORSTATIC for the first time. Keep returning that same brush for every WM_CTLCOLORSTATIC message:
HBRUSH hbrStaticBkg = NULL;
...
case WM_CTLCOLORSTATIC:
{
HDC hdc = (HDC) wParam;
SetTextColor(hdc, RGB(...));
if (!hbrStaticBkg) hbrStaticBkg = CreateSolidBrush(RGB(...));
return (LRESULT) hbrStaticBkg;
}
Destroy the brush only after you have destroyed the static text control.
DestroyWindow(hwndStatic);
if (hbrStaticBkg) {
DeleteObject(hbrStaticBkg);
hbrStaticBkg = NULL;
}
If you want to change the background color during the lifetime of the static text control, destroy the brush and invalidate the control to trigger a repaint, then create the new brush when requested.
COLOREREF clrStaticText = RGB(0,0,0);
COLORREF clrStaticBkg = RGB(255,255,255);
HBRUSH hbrStaticBkg = NULL;
...
case WM_CTLCOLORSTATIC:
{
HDC hdc = (HDC) wParam;
SetTextColor(hdc, clrStaticText);
if (!hbrStaticBkg) hbrStaticBkg = CreateSolidBrush(clrStaticBkg);
return (LRESULT) hbrStaticBkg;
}
...
clrStaticText = RGB(...);
clrStaticBkg = RGB(...);
if (hbrStaticBkg) {
DeleteObject(hbrStaticBkg);
hbrStaticBkg = NULL;
}
InvalidateRect(hwndStatic, NULL, TRUE);
How do I draw a line like this that is right next to a word like "Counts", in WinAPI with C?
Using Dialog Resources
Create a static text control with no text that is 1 or 2 pixels in height, turn on the border (WS_BORDER), and set its style to Static Edge (WS_EX_STATICEDGE). Then create a static text control with the word "Counts" in it on top of that. Then use CreateDialog() or DialogBox() to show the dialog box.
IDD_DIALOG1 DIALOGEX 0, 0, 172, 63
STYLE DS_SETFONT | DS_MODALFRAME | DS_FIXEDSYS | WS_POPUP | WS_CAPTION | WS_SYSMENU
CAPTION "Dialog"
FONT 8, "MS Shell Dlg", 400, 0, 0x1
BEGIN
LTEXT "",IDC_STATIC,6,12,156,1,WS_BORDER,WS_EX_STATICEDGE
LTEXT "Counts ",IDC_STATIC,6,8,26,8
END
Note: This is verbatim what Visual Studio generated using the dialog designer.
Creating Static Controls Using CreateWindow() (as suggested by Jonathan Potter)
LRESULT OnCreate( HWND hWnd, LPCREATESTRUCT lpCreateStruct )
{
// Get default gui font
NONCLIENTMETRICS metrics;
metrics.cbSize = sizeof(NONCLIENTMETRICS);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &metrics, NULL);
HFONT hFont = CreateFontIndirect(&metrics.lfMessageFont);
// Create the line
CreateWindowEx(WS_EX_STATICEDGE, _T("STATIC"), NULL, WS_CHILD|WS_VISIBLE|WS_BORDER,
10, 17, 280, 1, hWnd, NULL, lpCreateStruct->hInstance, NULL);
// Create the Counts label
HWND hwndCounts = CreateWindow(_T("STATIC"), _T("Counts "), WS_CHILD|WS_VISIBLE,
10, 10, 50, 26, hWnd, NULL, lpCreateStruct->hInstance, NULL);
// Apply the default gui font
SendMessage(hwndCounts, WM_SETFONT, (WPARAM)hFont, TRUE);
// Cleanup the font object
DeleteObject(hFont);
}
Drawing manually on the WM_PAINT event
void OnPaint( HWND hWnd )
{
// Get the default font
NONCLIENTMETRICS metrics;
metrics.cbSize = sizeof(NONCLIENTMETRICS);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &metrics, NULL);
HFONT hFont = CreateFontIndirect(&metrics.lfMessageFont);
// Setup HDC
RECT rect;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// Select the default font
SelectObject(hdc, hFont);
// Draw the line using the button shadow
SelectObject(hdc, GetStockObject(DC_PEN));
SetDCPenColor(hdc, GetSysColor(COLOR_BTNSHADOW));
MoveToEx(hdc, 10, 17, NULL);
LineTo(hdc, 280, 17);
// Draw the word Counts overtop of the line
SetRect(&rect, 10, 10, 280, 22);
SetTextColor(hdc, GetSysColor(COLOR_BTNTEXT));
SetBkColor(hdc, GetSysColor(COLOR_BTNFACE));
DrawText(hdc, TEXT("Counts "), -1, &rect, DT_NOCLIP);
// Cleanup the font object
DeleteObject(hFont);
// Quit painting
EndPaint(hWnd, &ps);
}
Note: Something I did not account for in this example is the height of the default font. You will want to adjust the code for that.
Here is a screenshot of the output of this method.
In your example, it looked like a single one pixel line, so that's what I drew, but if you'd like to make the line look more like a 'Fixed 3D' or 'lowered bevel line' (which is what the group box tends to draw for it's border line), then you can draw another line below it with the button highlight color.
SetDCPenColor(hdc, GetSysColor(COLOR_BTNHIGHLIGHT));
MoveToEx(hdc, 10, 18, NULL);
LineTo(hdc, 280, 18);
As pointed out by Ben Voigt, it might be better to do this with DrawEdge though.
RECT line;
SetRect(&line, 10, 17, 280,17);
DrawEdge(hdc, &line, EDGE_ETCHED, BF_TOP );
Creating a Group Box Control (suggested by Hans Passant)
Hans Passant's suggestion of doing this with a Group Box did work when I tested it. It still drew a rectangle, and when you enabled visual styles it was very difficult to see. Nevertheless, this should get you started if you want to give it a go.
HWND hwndGroup = CreateWindow(_T("Button"), _T("Counts "),
WS_CHILD|WS_VISIBLE|BS_GROUPBOX, 10, 10, 280, 2, hWnd, NULL,
lpCreateStruct->hInstance, NULL);
SendMessage(hwndGroup, WM_SETFONT, (WPARAM)hFont, TRUE);
Additional Note
Something else I would like to suggest is that you use can use Spy++ which comes with Visual Studio to analyze the window you are looking at. This will tell you at the very least if it's a child control, or whether they are painting it manually. If it's a child control you will also be able to see the rectangle and styles that are applied to it, as well lots of additional information.
Normally, even when using double buffering, when resizing a window, it seems that it's inevitable that the flickering will happen.
Step 1, the original window.
Step 2, the window is resized, but the extra area hasn't been painted.
Step 3, the window is resized, and the extra area has been painted.
Is it possible somehow to hide setp 2? Can I suspend the resizing process until the painting action is done?
Here's an example:
#include <Windows.h>
#include <windowsx.h>
#include <Uxtheme.h>
#pragma comment(lib, "Uxtheme.lib")
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
BOOL MainWindow_OnCreate(HWND hWnd, LPCREATESTRUCT lpCreateStruct);
void MainWindow_OnDestroy(HWND hWnd);
void MainWindow_OnSize(HWND hWnd, UINT state, int cx, int cy);
void MainWindow_OnPaint(HWND hWnd);
int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX wcex = { 0 };
HWND hWnd;
MSG msg;
BOOL ret;
wcex.cbSize = sizeof(wcex);
wcex.lpfnWndProc = WindowProc;
wcex.hInstance = hInstance;
wcex.hIcon = (HICON)LoadImage(NULL, IDI_APPLICATION, IMAGE_ICON, 0, 0, LR_SHARED);
wcex.hCursor = (HCURSOR)LoadImage(NULL, IDC_ARROW, IMAGE_CURSOR, 0, 0, LR_SHARED);
wcex.lpszClassName = TEXT("MainWindow");
wcex.hIconSm = wcex.hIcon;
if (!RegisterClassEx(&wcex))
{
return 1;
}
hWnd = CreateWindow(wcex.lpszClassName, TEXT("CWin32"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, HWND_DESKTOP, NULL, hInstance, NULL);
if (!hWnd)
{
return 1;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
while ((ret = GetMessage(&msg, NULL, 0, 0)) != 0)
{
if (ret == -1)
{
return 1;
}
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
HANDLE_MSG(hWnd, WM_CREATE, MainWindow_OnCreate);
HANDLE_MSG(hWnd, WM_DESTROY, MainWindow_OnDestroy);
HANDLE_MSG(hWnd, WM_SIZE, MainWindow_OnSize);
HANDLE_MSG(hWnd, WM_PAINT, MainWindow_OnPaint);
default:
return DefWindowProc(hWnd, uMsg, wParam, lParam);
}
}
BOOL MainWindow_OnCreate(HWND hWnd, LPCREATESTRUCT lpCreateStruct)
{
BufferedPaintInit();
return TRUE;
}
void MainWindow_OnDestroy(HWND hWnd)
{
BufferedPaintUnInit();
PostQuitMessage(0);
}
void MainWindow_OnSize(HWND hWnd, UINT state, int cx, int cy)
{
InvalidateRect(hWnd, NULL, FALSE);
}
void MainWindow_OnPaint(HWND hWnd)
{
PAINTSTRUCT ps;
HPAINTBUFFER hpb;
HDC hdc;
BeginPaint(hWnd, &ps);
hpb = BeginBufferedPaint(ps.hdc, &ps.rcPaint, BPBF_COMPATIBLEBITMAP, NULL, &hdc);
FillRect(hdc, &ps.rcPaint, GetStockBrush(DKGRAY_BRUSH));
Sleep(320); // This simulates some slow drawing actions.
EndBufferedPaint(hpb, TRUE);
EndPaint(hWnd, &ps);
}
Is it possible to eliminate the flickering?
When the window is updated during a drag operation, then the OS has to show something in the extended window region. If you can't provide anything then it will show the background until you do. Since you didn't specify any background you get blackness. Surely you ought to be specifying a background brush? Simply adding the following to your code makes the behaviour more palatable:
wcex.hbrBackground = GetStockBrush(DKGRAY_BRUSH);
However, if you take as long as 320ms to respond to a WM_PAINT then you ruin the resize UI for the user. It becomes jerky and unresponsive. The system is designed around the assumption that you can paint the window quickly enough for dragging to feel smooth. The right way to fix your problem is to make WM_PAINT run in a reasonable time.
If you really can't achieve quick enough painting for smooth dragging then I suggest a couple of alternatives:
Disable window updates during dragging. I'm sure this can be done for individual windows, but I can't remember how to do it off the top of my head.
Paint something fake whilst a resize/drag is active, and postpone the real painting until when the resize/drag has completed. Listening for WM_ENTERSIZEMOVE and WM_EXITSIZEMOVE are the keys to this. This Microsoft sample program illustrates how to do that: https://github.com/microsoft/Windows-classic-samples/blob/master/Samples/Win7Samples/winui/fulldrag/
Use WM_SIZING instead of WM_SIZE and don't forget about WM_ERASEBKGND.
If you go into the System Properties control panel applet, choose the Advanced tab, and then click Settings... in the Performance group box, you'll see a checkbox setting called Show window contents while dragging. If you uncheck that and try resizing a window, you'll see that only the window frame moves until you complete the drag operation, and then the window repaints just once at the new size. This is how window sizing used to work when we had slow, crufty computers.
Now we don't really want to change the setting globally (which you would do by calling SystemParametersInfo with SPI_SETDRAGFULLWINDOWS, but don't really do that because your users won't like it).
What happens when the user grabs the resize border is that the thread enters a modal loop controlled by the window manager. Your window will get WM_ENTERSIZEMOVE as that loop begins and WM_EXITSIZEMOVE when the operation is complete. At some point you'll also get a WM_GETMINMAXINFO, which probably isn't relevant to what you need to do. You'll also get WM_SIZING, WM_SIZE messages rapidly as the user drags the sizing frame (and the rapid WM_SIZEs often lead to WM_PAINTs).
The global Show window contents while dragging setting is responsible for getting the rapid WM_SIZE messages. If that setting is off, you'll just get one WM_SIZE message when it's all over.
If your window is complicated, you probably have layout code computing stuff (and maybe moving child windows) in the WM_SIZE handler and a lot of painting code in the WM_PAINT handler. If all that code is too slow (as your sample 320 ms delay suggests), then you'll have a flickery, jerky experience.
We really don't want to change the global setting, but it does inspire a solution to your problem:
Do simpler drawing during the resize operation and then do your (slower) complex drawing just once when the operation is over.
Solution:
Set a flag when you see the WM_ENTERSIZEMOVE.
Change your WM_SIZE handler to check the flag and do nothing if it's set.
Change your WM_PAINT handler to check the flag and do a simple, fast fill of the window in a solid color if it's set.
Clear the flag when you see WM_EXITSIZEMOVE, and then trigger your layout code and invalidate your window so that everything gets updated based on the final size.
If your slow window is a child rather than your application's top-level window, you'll have to signal the child window when the top-level window gets the WM_ENTERSIZEMOVE and WM_EXITSIZEMOVE in order to implement steps 1 and 4.
Yes you can entirely delete flickering :)
You can do all the window message handling in one thread, and painting its context in another. Your window always keeps responsive. It works great, can not understand why this is not established best practice.
If you bind a Direct3D context for example, it can have an instant scaling while resizing, completely without having the context updated!
My code looks like this:
int WINAPI wWinMain( HINSTANCE a_hInstance, HINSTANCE a_hPrevInstance, LPWSTR a_lpCmdLine, int a_nCmdShow )
{
Win32WindowRunnable* runnableWindow=new Win32WindowRunnable(a_hInstance, a_nCmdShow);
IThread* threadWindow=new Win32Thread(runnableWindow);
threadWindow->start();
Scene1* scene=new Scene1(runnableWindow->waitForWindowHandle());
IThread* threadRender=new Win32Thread(scene);
threadRender->start();
threadWindow->join();
threadRender->pause();
threadRender->kill();
delete runnableWindow;
return 0;
}
Full source example here:
https://github.com/TheWhiteAmbit/TheWhiteAmbit/blob/master/Win32App/Win32Main.cpp
So i'm painting a bitmap, heres my code:
hdcMem = CreateCompatibleDC(hdc);
SelectObject(hdcMem, g_hBitmap);
GetObject(g_hBitmap, sizeof(bm), &bm);
BitBlt(hdc, 196 - (bm.bmWidth/2), 90, bm.bmWidth, bm.bmHeight, hdcMem, 0, 0, SRCCOPY);
DeleteDC(hdcMem);
Sometimes, when I paint it with this code, the bitmap is not displayed. Although if i minimize/unminimize the window, the bitmap is displayed. I'm pretty sure there's no problems with my code so is there something else I should be doing?
EDIT:
Turns out it's not just bitmaps, if I draw text with TextOut sometimes it's not displayed until its minimized/unminimized. I don't think minimizing/unminimizing sends another WM_PAINT message, so I don't think that when i do that it's causing it to be repainted correctly.
Oh and the rest of the controls get painted normally, just the stuff inside WM_PAINT isn't painted.
UPDATEHere's the code thats causing the problems, it works 98% of the time too.
// This is a global variable
bool GlobalVar = false;
// This is a different thread started with _beginthread
void ThreadExample()
{
GlobalVar = true;
InvalidateRect(hMainWnd, NULL, TRUE);
_endthread();
}
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
if (GlobalVar == true)
{
SetBkMode(hdc, TRANSPARENT);
SetTextColor(hdc, 0x0000ff);
OrigFont = SelectObject(hdc, g_hLargeFont);
GetTextExtentPoint32(hdc, ErrorMsg, lstrlen(ErrorMsg), &sz);
TextOut(hdc, 196 - (sz.cx/2), 100, ErrorMsg, lstrlen(ErrorMsg));
SelectObject(hdc, OrigFont);
}
EndPaint(hWnd, &ps);
break;
EDIT2:Another important detail could be, in my actual application, this code is inside a if statement that checks a global variable, and paints if its true. And this variable is set from a different thread, and after the variable is set I call InvalidateRect(hMainWnd, NULL, TRUE);
Updated my example code to represent this.
What is immediately not good with this code snippet (you actually should rather have posted more details) is that you delete temporary DC with your global bitmap handle still selected into it. You need to do SelectObject once again to unselect your bitmap.
You normally do it like this:
HGDIOBJ hPreviousBitmap = SelectObject(hdcMem, g_hBitmap);
// ...
SelectObject(hdcMem, hPreviousBitmap);
Also, error checking never hurts. Possibly one of the API calls fail and it's important which one exactly as it sheds more light on the issue.
I want to display an image in OpenCV in a full screen borderless window.
In other words, only the image pixels will appear, without menu, toolbar, or window background.
Using imshow() or cvShowImage() don't enable it:
The window grows to be full screen
in width but not in height. It misses few pixels.
I could not make it borderless even by changing settings of window
handler.
I think that the problem is rooted in cvNamedWindow() method which creates main WS_OVERLAPPED window, then creates a child and all functions like imshow() or cvGetWindowHandle() operate on the child.
Thus even windows command:
SetWindowLong((HWND)cvGetWindowHandle(winName), GWL_STYLE, WS_VISIBLE | WS_EX_TOPMOST | WS_POPUP);
Doesnt help, since the child cannot become borderless WS_POPUP. Someone got a workaround?
Maybe, showing opencv mat to window
without using opencv built in methods
Or some kind of windows trick
P.S. I tried the following code:
cvMoveWindow("AAA",0,0);
cvSetWindowProperty("AAA", CV_WINDOW_FULLSCREEN, CV_WINDOW_FULLSCREEN);
// Also I tried this:
HWND hwnd = (HWND)cvGetWindowHandle("AAA");
RECT windowRect;
windowRect.left = 0;
windowRect.top = 0;
windowRect.right = cxScreen; //Display resolution
windowRect.bottom = cyScreen; //Display resolution
AdjustWindowRect(&windowRect,WS_VISIBLE,false);
long p_OldWindowStyle = SetWindowLongPtr(hwnd,GWL_STYLE,WS_POPUP);
SetWindowPos(hwnd,HWND_TOP,0,0,windowRect.right,windowRect.bottom,SWP_FRAMECHANGED | SWP_SHOWWINDOW);
SetWindowLong(hwnd, GWL_STYLE, WS_VISIBLE | WS_EX_TOPMOST | WS_POPUP);
Have you issued cvShowImage() to display the window? Because it seems you are not doing it. Anyway, you might want to call the win32 API for this instead, so add a call to ShowWindow(hwnd, SW_SHOW); after SetWindowPos().
If your current call to SetWindowPos() doesn't do the trick, check this answer: Hide border of window, if i know a handle of this window
I recommend you doing your tests without calling cvSetWindowProperty() at first, just to make sure you can find a method that works.
Just a note, if you check modules/highgui/src/window_w32.cpp you can see how OpenCV creates windows on Windows.
EDIT:
The following code implements the tips I gave before and bypasses the problems the OP reported. The trick is NOT using cvGetWindowHandle() to retrieve the windows' handle and use directly win32 API for that: FindWindow()
IplImage* cv_img = cvLoadImage("test.jpg", CV_LOAD_IMAGE_UNCHANGED);
if(!cv_img)
{
printf("Failed cvLoadImage\n");
return -1;
}
cvNamedWindow("main_win", CV_WINDOW_AUTOSIZE);
cvMoveWindow("main_win", 0, 0);
cvSetWindowProperty("main_win", CV_WINDOW_FULLSCREEN, CV_WINDOW_FULLSCREEN);
cvShowImage("main_win", cv_img);
//HWND cv_hwnd = (HWND)cvGetWindowHandle("main_win");
//if (!cv_hwnd)
//{
// printf("Failed cvGetWindowHandle\n");
//}
//printf("cvGetWindowHandle returned %p\n", *cv_hwnd);
HWND win_handle = FindWindow(0, L"main_win");
if (!win_handle)
{
printf("Failed FindWindow\n");
}
SetWindowLong(win_handle, GWL_STYLE, GetWindowLong(win_handle, GWL_EXSTYLE) | WS_EX_TOPMOST);
ShowWindow(win_handle, SW_SHOW);
cvWaitKey(0);
cvReleaseImage(&cv_img);
cvDestroyWindow("main_win");
This code will make the window created by OpenCV borderless, but you still might have to tweak one thing or another to make this operation perfect. You'll see why. One idea is to resize the window and make it the size of the image.
EDIT:
Well, since you stated:
writing a demo might be very hard
I also decided to do this last part for you, since I'm such a nice guy =]
This is a small improvement of the code above:
HWND win_handle = FindWindow(0, L"main_win");
if (!win_handle)
{
printf("Failed FindWindow\n");
}
// Resize
unsigned int flags = (SWP_SHOWWINDOW | SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER);
flags &= ~SWP_NOSIZE;
unsigned int x = 0;
unsigned int y = 0;
unsigned int w = cv_img->width;
unsigned int h = cv_img->height;
SetWindowPos(win_handle, HWND_NOTOPMOST, x, y, w, h, flags);
// Borderless
SetWindowLong(win_handle, GWL_STYLE, GetWindowLong(win_handle, GWL_EXSTYLE) | WS_EX_TOPMOST);
ShowWindow(win_handle, SW_SHOW);
And on my system it displays exactly what you asked on the question.