I register the window class like this:
WNDCLASSEX wctt;
wctt.cbSize = sizeof(WNDCLASSEX);
wctt.style = CS_DBLCLKS;
wctt.lpfnWndProc = WndProcTooltip;
wctt.cbClsExtra = 0;
wctt.cbWndExtra = 0;
wctt.hInstance = m_hAppInstance;
wctt.hIcon = NULL;
wctt.hCursor = LoadCursor(NULL, IDC_SIZE);
wctt.hbrBackground = NULL;
wctt.lpszMenuName = NULL;
wctt.lpszClassName = _T("myWindow");
wctt.hIconSm = NULL;
RegisterClassEx(&wctt)
As you can see I use wctt.hbrBackground = NULL; so it will have no background.
The window is created like this:
::CreateWindowEx(WS_EX_TOPMOST | WS_EX_TOOLWINDOW,
_T("myWindow"),
NULL,
WS_VISIBLE | WS_POPUP,
50,
50,
150,
100,
NULL,
NULL,
m_hAppInstance,
NULL);
In the paint section I draw icon on the window:
PAINTSTRUCT ps;
HDC hdc;
BITMAP bitmap;
ICONINFO iconinfo;
hdc = ::BeginPaint(hWnd, &ps);
::SetBkMode(hdc,TRANSPARENT);
::GetIconInfo(localIcon, &iconinfo);
::GetObject(iconinfo.hbmColor, sizeof(bitmap), &bitmap);
::DeleteObject(iconinfo.hbmColor);
::DeleteObject(iconinfo.hbmMask);
::DrawIconEx(hdc, 0,0, localIcon, bitmap.bmWidth, bitmap.bmHeight, 0, NULL, DI_NORMAL);
The icon size is smaller than the window size and I get on the background the current view on the window below the popup.
But now when I move the window (or minimize the window below the popup) the background is not changing.
I was trying to make a timer that each time do the flowing:
RECT rcClient;
GetClientRect(hWnd, &rcClient);
InvalidateRect(hWnd,&rcClient,TRUE);
This makes the print function run again but the background of the icon is not changing.
Should I do anything in WM_ERASEBKGND?
Does Anyone have any idea how to make it work?
thanks,
guy
It's not enough to just let the background stay unpainted; you also need to get the window below yours to repaint itself when necessary.
If the windows are part of the same hierarchy, created by the same thread, it is sufficient to give your window the WS_EX_TRANSPARENT extended style. This causes the window underneath to paint itself first so the background is always up-to-date.
Otherwise you need to use SetWindowRgn so that your window actually doesn't exist outside of the borders you wish to paint.
Look at Layered Window. This feature allows creating semi-transparent windows of different shapes.
Add WS_EX_LAYERED extended attribute in your window class.
You can control the transparency of your window with these two functions:
SetLayeredWindowAttributes:
bAlpha controls the opacity of the entire window, if you pass LWA_ALPHA in dwFlags.
When bAlpha is 0, the window is completely transparent. When bAlpha is 255, the window is opaque.
crKey sets the color that would transparent.
All pixels painted by the window in this color will be transparent.
UpdateLayeredWindow gives you precise control over window transparency, you can give different parts of window different levels of transparency.
If you're trying to create a non-rectangular window, this is not sufficient. Setting "no background" simply means the background will not be drawn, and you'll see whatever happens to be in memory at that location.
To create a non-rectangular window, have a look at the SetWindowRgn function.
Related
What do I want to achive:
I want to create a window that behaves like a WS_OVERLAPPEDWINDOW | WS_SIZEBOX(can be minimized, maximized, closed from system context menu on Alt+Space, supports Window Snapping, has shadow if it is enabled in system Performance Options -> [x] Enable shadow under window and so on). It also should be borderless (without title bar, icon, application name in title bar and so on), just client region and nothing else.
So main goals are:
Has no border;
Supports default window functionality;
Drops shadow underneath.
Don't say that it is impossible. The most simple example of such a window is Telegram Desktop. They use Qt library. Don't say I should use it. I want to learn how they did this trick. Their window is borderless, without bugs (that are described below). I know that Qt uses OpenGL inside for their window. But I also know that it should be possible to draw with GDI+ only without OpenGL.
What I have already tried:
github:melak47/BorderlessWindow This window has a tiny border around. You can see it if you resize it really quickly holding by the top or left edge of the window. We can also set margins to be like MARGINS m{0,0,0,1} for DwmExtendFrameIntoClientArea(hWnd, &m);. But window will still remain the same border which could be seen if resize.
github:rossy/borderless-window This solution is better. It propose two variants to struggle with this problem.
The border here is hidden by enabling WS_EX_LAYERED window style with chroma keying by color (e.g. magenta). But it is obvious that now we need to perform checks every time we draw something on bitmap for a specified chroma color. If user draws clear magenta RGB(255, 0, 255) we can then replace it with RGB(254, 0, 255) to avoid holes inside. But I think it is a very bad solution that cause unneccessary checks for each pixel in bitmap.
The border is now considered as a part of client area. We disable WM_EX_LAYERED and color keying and using GDI+ to draw transparent colors on top border. The this is that you can't draw pure opaque color on this border (e.g. graphics.FillRect(&Gdiplus::SolidBrush{Gdiplus::Color{255, 255, 0, 0}}, Gdiplus::Rect{0, 0, windowWidht, windowHeight}) will not cover top border by red color - the border will be white or another color (I don't know what it depends on but I think it is window system color preference, like Personalize -> Colors -> [x] Title bars and window borders)). By the way you can cover it any color you want just by setting opacity of this color to 254. This will work. But the problem is still there: if we'll try to resize the window guess what.. we have this white border on top (or what you set this when MARGINS m{0,0,0,1} for DwmExtendFrameIntoClientArea(hWnd, &m);. And also notice that it will be a lot of pain when you will forget that you can't draw pure opaque color and draw something with GDI. So I come up to the next solution.
My idea is to draw with alpha value of 254 only the top most scanline of bitmap. Becase I also perform double buffering I can do it with AlphaBlend(hdc, 0, 0, width, 1, memHdc, 0, 0, width, 1, {AC_SRC_OVER, 0, 254, AC_SRC_ALPHA});. But this solution is still got it's own bug. When resize window we still got this border because it's been drawn faster than our window content. Also we got weird pixels on the left side if we resize the window by the top edge. And the last bug is that this alpha dissapears sometimes to and the top border is visible not only in undrawn client regions but also on top of validated regions.
The code of WM_PAINT procedure:
LRESULT wmPaint(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps = {};
HDC hdc = BeginPaint(hWnd, &ps);
auto [width, height] = dimensions.normal;
HDC memHdc = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, width, height);
SelectObject(memHdc, hBitmap);
// Children perform their drawings on "back buffer" - memDc
handleChildrenDraw(memDc);
// Copy top line as transparent and other as always to paint over non-client area as it was client
BLENDFUNCTION bf = {};
bf.BlendOp = AC_SRC_OVER;
bf.SourceConstantAlpha = 254;
bf.AlphaFormat = AC_SRC_ALPHA;
auto alphaSuccess = AlphaBlend(hdc, 0, 0, width, 1, memHdc, 0, 0, width, 1, bf);
expect(alphaSuccess == TRUE);
auto copySuccess = BitBlt(hdc, 1, 0, width, height, memHdc, 1, 0, SRCCOPY);
expect(copySuccess == TRUE);
EndPaint(hWnd, &ps);
DeleteObject(memHdc);
DeleteObject(hBitmap);
return 0;
}
Sreenshot: window rendered with a white srtipe on top (border has been rendered for some reasons)
Question:
Can you please tell me how to fix this top border drawing bug or any better solution to draw borderless window with WinAPI? Thanks in advance.
I have window with gradient background. Combobox have own background brush.
How can I remove white corner in combobox? How can I change brush or another way.
On picture white corner marked by red frame.
I create combobox as:
DWORD dwStyle = WS_CHILD | CBS_DROPDOWNLIST;
if (m_bVisible) dwStyle |= WS_VISIBLE;
m_hWnd = CreateWindow(WC_COMBOBOX, NULL, dwStyle,
m_posX, m_posY, m_width, m_height, m_hParent, (HMENU)m_id, m_hInstance, NULL);
I tried changing background brush with message WM_CTLCOLOREDIT, but no effect:
case WM_CTLCOLOREDIT:
if ((HWND)lParam == m_hSrcListBox)
{
return (LRESULT)m_hBrush;
}
break;
=== SOLVED. WORK VERSION ===
First way.
In parent WndProc:
case WM_CTLCOLORSTATIC:
if ((HWND)lParam == m_hSrcListBox)
{
return (LRESULT)m_pSrcListBox->GetHbrush();
}
break;
In my class:
//
// CListBox::GetHbrush().
//
// Get brush.
//
HBRUSH CListBox::GetHbrush()
{
if (!m_hBrush)
{
m_hBrush = CreateTransparentBackgroundBrush(m_hParent, m_hWnd);
}
return m_hBrush;
}
Create transparent background:
//
// CListBox::CreateTransparentBackgroundBrush().
//
// Create transparent background for element.
//
HBRUSH CListBox::CreateTransparentBackgroundBrush(HWND parent, HWND client)
{
RECT rct;
POINT p1;
POINT p2;
GetWindowRect(client, &rct);
p1.x = rct.left;
p1.y = rct.top;
ScreenToClient(parent, &p1);
p2.x = rct.right;
p2.y = rct.bottom;
ScreenToClient(parent, &p2);
HDC hdcParent = GetDC(parent);
HDC hdcClient = GetDC(client);
HDC hdcmem = CreateCompatibleDC(hdcClient);
HBITMAP hbitmap = CreateCompatibleBitmap(hdcClient, p2.x - p1.x, p2.y - p1.y);
SelectObject(hdcmem, hbitmap);
BitBlt(hdcmem, 0, 0, p2.x - p1.x, p2.y - p1.y, hdcParent, p1.x, p1.y, SRCCOPY);
HBRUSH pattern = CreatePatternBrush(hbitmap);
DeleteDC(hdcmem);
DeleteObject(hbitmap);
ReleaseDC(client, hdcClient);
ReleaseDC(parent, hdcParent);
return pattern;
}
Second way.
In parent WndProc draw background in WM_ERASEBKGND message, then the corners will not.
case WM_ERASEBKGND:
m_hdc = (HDC)wParam;
// draw background.
return TRUE;
break;
The result of both methods:
For dialog boxes, handle WM_CTLCOLORDLG and return a background brush for the combobox
If you are displaying this combobox in a dialog, the trick is actually to handle the WM_CTLCOLORDLG message in your dialog's window procedure. In response to this message, you return a handle to a brush that the dialog box will use to paint its background.
case WM_CTLCOLORDLG:
{
// NOTE: This code is wrong because it creates a new brush object each time it processes
// the message, which it promptly leaks. It is merely for demonstration purposes.
// Normally, you would create the brush once, in response to WM_INITDIALOG,
// cache it away, and return that same cached handle each time, finally destroying
// the brush in response to WM_NCDESTROY.
HBRUSH hBrush = CreateSolidBrush(RGB(255, 120, 0));
return reinterpret_cast<INT_PTR>(hBrush);
}
This is the standard, documented way of changing the background color of a dialog box, and it also solves the problem with the combobox. Apparently, for whatever reason, combobox controls also use this brush to paint their background. I suppose they send a WM_CTLCOLORDLG message to their parent when they are painting themselves.
Of course, this limits you to the graphics capabilities of a GDI brush. You can draw any system or solid color that you want, or even use a hatch or pattern/bitmap brush, but there is no simple way of creating a gradient brush. (GDI+ has one, but not GDI.) Normally it wouldn't matter—you'd just call the GradientFill function in your WM_PAINT (or even WM_ERASEBKGND) message handler. That works fine for the dialog's background, but the combobox still draws its background with the brush returned by WM_CTLCOLORDLG, so it still has those 4 dots on its corners drawn in COLOR_3DFACE (which is the brush that the default dialog procedure returns).
Returning a null brush (NULL_BRUSH/HOLLOW_BRUSH) from WM_CTLCOLORDLG doesn't work, either. It changes the appearance slightly, such that the upper-right and lower-left corner pixels are now filled with something that looks like COLOR_3DSKSHADOW, but they are still visibly filled with a color other than the actual background gradient.
So if you really want it to look nice, you are left with only a single option: returning a handle to a GDI brush. And of course, it needs to be the same brush as is used to draw the dialog's background.
If you want a gradient fill, the only solution I can think of is using a pattern/bitmap brush, where the bitmap (DDB or DIB) is your gradient. Not great, but at least the days of Windows 9x limiting us to 8×8 patterns are long gone. Maybe someone more inventive than me can use this information to think of a better workaround?
For other windows, handle WM_CTLCOLORSTATIC and return a background brush for the combobox
All of that for a dialog box. But what about if you are displaying the combobox in a standard window (i.e., something other than a dialog box)? The WM_CTLCOLORDLG message is never sent in this case.
Instead, the combobox sends a WM_CTLCOLORSTATIC message to its parent window, and then uses the brush handle returned in response to that message to paint its background.
This is weird, I know. I only stumbled across it by conducting empirical tests, and I'm not sure quite sure what the rationale was. If I had to guess, I'd say that the CBS_DROPDOWNLIST style makes the combobox non-editable (i.e., it's not a true combobox because there is no Edit control), so instead of WM_CTLCOLOREDIT, it uses WM_CTLCOLORSTATIC. A disabled Edit box sends WM_CTLCOLORSTATIC, too, and so does a disabled combobox with the "normal" CBS_SIMPLE and CBS_DROPDOWN styles.
Weirder still, this only happens when the Aero theme is enabled (Vista and 7). It doesn't happen on Windows 10, or with the Luna theme (Visual Styles under XP), or with the Classic theme. (I didn't test on Windows 8 or 8.1.) Not that it matters, I suppose, since all of those other themes draw a simple rectangular combobox, leaving no corner pixels for the background to show through.
Whatever the logic, the solution remains to handle the WM_CTLCOLORSTATIC message and return the brush you wish the combobox to use to paint its background.
The same considerations apply here as those discussed above for the dialog box. If your window uses a solid-color background or a system color, you are home-free. Simply return a handle to the same brush that you set as the window class's background brush. If you want to use a gradient, you'll need to figure out a way to represent that gradient in the form of a GDI brush.
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDR_APPLICATION));
wcex.hIconSm = LoadIcon(hInstance, MAKEINTRESOURCE(IDR_APPLICATION_SMALL));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = reinterpret_cast<HBRUSH>(COLOR_3DDKSHADOW + 1); // background brush
wcex.lpszMenuName = NULL;
wcex.lpszClassName = TEXT("My Colored Window Class");
RegisterClassEx(&wcex);
case WM_CTLCOLORSTATIC:
{
// NOTE: No leak here because we're using a system brush in this example.
return reinterpret_cast<LRESULT>(GetSysColorBrush(COLOR_3DDKSHADOW)); // background brush
}
How can i remove white corner in combobox?
I don't know if there is a more official way to get rid of it, but one option would be to create a Region with rounded corners using CreateRoundRectRgn(), and then apply it to the ComboBox using SetWindowRgn(). That will mask off the corners.
Could you give the simplest way to achieve double buffering for this example code (to prevent flickering):
HWND hwnd = FindWindow(0, "Untitled - Notepad");
HDC hDC_Desktop = GetDC(hwnd);
...
while( )
{
RECT rect = { 10, 10, 10 + 50, 10 + 50 };
FillRect(hDC_Desktop, &rect, ColorBrush);
InvalidateRect (hwnd, NULL, TRUE);
}
The reason it's "flickering" is because the target window is getting invalidated and it is being redrawn. Since it's not your window - you don't necessarily have control over that.
If this was your own window there is a simple strategy to speed up your drawing speed and reduce flicker: Use a Memory DC to draw on and capture WM_ERASEBKGND to suppress background redraws.
In depth explanation and strategy for fixing it (in your application's window): http://www.catch22.net/tuts/win32/flicker-free-drawing
If your intent is to draw on another application, might I suggest creating a window on top of that application and draw on that.
Hi I have WNDCLASSEX structure which has this data:
m_wndClass.cbSize = sizeof(WNDCLASSEX);
m_wndClass.style = CS_NOCLOSE;
m_wndClass.lpfnWndProc = WndProc;
m_wndClass.cbClsExtra = 0;
m_wndClass.cbWndExtra = 0;
m_wndClass.hInstance = GetModuleHandle(NULL);
m_wndClass.hIcon = NULL;
m_wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
m_wndClass.hbrBackground = NULL;
m_wndClass.lpszMenuName = NULL;
m_wndClass.lpszClassName = Checkbox::CHECKBOX_CLASS.c_str();
m_wndClass.hIconSm = NULL;
I need to have window without background, because I need to draw text on parent window and text may be any color.
Drawing works fine, code for drawing:
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC dc = BeginPaint(window, &ps);
if (!classInfo->m_text.empty())
{
HDC wdc = GetDC(window);
SetBkMode(wdc,TRANSPARENT);
DrawText(wdc, classInfo->m_text.c_str(), -1, &classInfo->m_textRect, DT_CENTER | DT_VCENTER | DT_SINGLELINE | DT_NOCLIP);
ReleaseDC(window, wdc);
}
EndPaint(window, &ps);
break;
}
However I have method to change text of label:
void Checkbox::SetText(const String& text)
{
m_text = text;
SetTextRectSize(); //calculates size of RECT
if (m_window != NULL)
InvalidateRect(m_window, NULL, TRUE);
}
After I create window with label I see label, however if I want to change text on it, it doesn't change (I need to manualy resize window and it changes after that). However I hadn't have this problem at the time when I used to have colored background, for example my window class had this:
m_wndClass.hbrBackground = HBRUSH(COLOR_3DFACE+1);
I want to ask, how to update window which, has no background.
EDIT: I have tried some stuff
FillRect(dc, &rect, (HBRUSH)GetStockObject(NULL_BRUSH));
also tried to change window procedure:
case WM_CTLCOLORSTATIC:
{
HDC hdc = (HDC) wp;
SetBkMode (hdc, TRANSPARENT);
return (LRESULT)GetStockObject(NULL_BRUSH);
}
And the result is that I draw new text on previous, after setting text into some longer text part of label becomes corupted! see this but after resizing the main window my label becomes readable.
Your code doesn't set the device context's text foreground color for DrawText(), although the default is black. See SetTextColor().
SetBkMode(..., TRANSPARENT) just sets the background color/mode for the DrawText() rect, not the entire window.
You are asking about how to draw the window so it is transparent, but the problem isn't with the drawing at all.
The answer is essentially that everything you have done so far towards making a transparent window is wrong. It looks like the window is transparent, but in fact it is not, as you can see from the behaviour you describe when you move and resize the window. That's the classic symptom.
In other words, you haven't made the window transparent, you have just stopped drawing the background. What you see as the background is just whatever happened to be underneath the window when it was first drawn.
You need make a Layered window. To find out how to make transparent windows, go here:
http://msdn.microsoft.com/en-us/library/ms997507.aspx
Do you want Text/Check/Label be transparent on parent form?
You can Add WS_CLIPSIBLINGS and WS_EX_TRANSPARENT..
Use SetBkMode(hDC, TRANSPARENT) When WM_PAINT message
I'm creating what should be a very simple Win32 C++ app whose sole purpose it to ONLY display a semi-transparent PNG. The window shouldn't have any chrome, and all the opacity should be controlled in the PNG itself.
My problem is that the window doesn't repaint when the content under the window changes, so the transparent areas of the PNG are "stuck" with what was under the window when the application was initially started.
Here's the line where I setup the new window:
hWnd = CreateWindowEx(WS_EX_TOPMOST, szWindowClass, szTitle, WS_POPUP, 0, height/2 - 20, 40, 102, NULL, NULL, hInstance, 0);
For the call to RegisterClassEx, I have this set for the background:
wcex.hbrBackground = (HBRUSH)0;
Here is my handler for WM_PAINT message:
case WM_PAINT:
{
hdc = BeginPaint(hWnd, &ps);
Gdiplus::Graphics graphics(hdc);
graphics.DrawImage(*m_pBitmap, 0, 0);
EndPaint(hWnd, &ps);
break;
}
One thing to note is that the application is always docked to the left of the screen and doesn't move. But, what's underneath the application may change as the user opens, closes or moves windows under it.
When the application first starts, it looks perfect. The transparent (and simi-transparent) parts of the PNG show through perfectly. BUT, when the background underneath the application changes, the background DOESN'T update, it just stays the same from when the application first started. In fact, WM_PAINT (or WM_ERASEBKGND does not get called when the background changes).
I've been playing with this for quite a while and have gotten close to getting 100% right, but not quite there. For instance, I've tried setting the background to (HBRUSH) NULL_BRUSH and I've tried handling WM_ERASEBKGND.
What can be done to get the window to repaint when the contents under it changes?
I was able to do exactly what I wanted by using the code from Part 1 and Part 2 of this series:
Displaying a Splash Screen with C++
Part 1: Creating a HBITMAP archive
Part 2: Displaying the window archive
Those blog posts are talking about displaying a splash screen in Win32 C++, but it was almost identical to what I needed to do. I believe the part that I was missing was that instead of just painting the PNG to the window using GDI+, I needed to use the UpdateLayeredWindow function with the proper BLENDFUNCTION parameter. I'll paste the SetSplashImage method below, which can be found in Part 2 in the link above:
void SetSplashImage(HWND hwndSplash, HBITMAP hbmpSplash)
{
// get the size of the bitmap
BITMAP bm;
GetObject(hbmpSplash, sizeof(bm), &bm);
SIZE sizeSplash = { bm.bmWidth, bm.bmHeight };
// get the primary monitor's info
POINT ptZero = { 0 };
HMONITOR hmonPrimary = MonitorFromPoint(ptZero, MONITOR_DEFAULTTOPRIMARY);
MONITORINFO monitorinfo = { 0 };
monitorinfo.cbSize = sizeof(monitorinfo);
GetMonitorInfo(hmonPrimary, &monitorinfo);
// center the splash screen in the middle of the primary work area
const RECT & rcWork = monitorinfo.rcWork;
POINT ptOrigin;
ptOrigin.x = 0;
ptOrigin.y = rcWork.top + (rcWork.bottom - rcWork.top - sizeSplash.cy) / 2;
// create a memory DC holding the splash bitmap
HDC hdcScreen = GetDC(NULL);
HDC hdcMem = CreateCompatibleDC(hdcScreen);
HBITMAP hbmpOld = (HBITMAP) SelectObject(hdcMem, hbmpSplash);
// use the source image's alpha channel for blending
BLENDFUNCTION blend = { 0 };
blend.BlendOp = AC_SRC_OVER;
blend.SourceConstantAlpha = 255;
blend.AlphaFormat = AC_SRC_ALPHA;
// paint the window (in the right location) with the alpha-blended bitmap
UpdateLayeredWindow(hwndSplash, hdcScreen, &ptOrigin, &sizeSplash,
hdcMem, &ptZero, RGB(0, 0, 0), &blend, ULW_ALPHA);
// delete temporary objects
SelectObject(hdcMem, hbmpOld);
DeleteDC(hdcMem);
ReleaseDC(NULL, hdcScreen);
}
Use the SetLayeredWindowAttributesarchive function, this allows you to set a mask color that will become transparent, thus allowing the background to show through.
You will also need to configure your window with the layered flag, e.g.:
SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED);
After that it's fairly simple:
// Make red pixels transparent:
SetLayeredWindowAttributes(hwnd, RGB(255,0,0), 0, LWA_COLORKEY);
When your PNG contains semi-transparent pixels that you want to blend with the background, this becomes more complicated. You could try looking at the approach in this CodeProject article:
Cool, Semi-transparent and Shaped Dialogs with Standard Controls for Windows 2000 and Above