I have a buffer of pixel represented as uint8_t buffer[width * height * PIXEL_SIZE] that i would like to regularly modify the content data and redraw the buffer into the window.
I'm encoutering two issues with the winapi with which one i'm lost :
I have made many researchs but no code snippet have successfully helped me to solve my issue.
Here is a not working code sample in order to show what i would like to archieve with the elements of code i have:
// Global variables
static HDC hdc;
static HDC context_hdc;
static HBITMAP hDib;
static HGDIOBJ obj;
static void set_bmi_object(BITMAPINFO *bmi, int width, int height) {
memset(bmi, 0, sizeof(BITMAPINFO));
bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi->bmiHeader.biWidth = width;
bmi->bmiHeader.biHeight = -height;
bmi->bmiHeader.biPlanes = 1;
bmi->bmiHeader.biBitCount = 32;
bmi->bmiHeader.biCompression = BI_RGB;
}
// Allocate a new image buffer
void *new_image(HWND hwnd, int width, int height)
{
BITMAPINFO bmi;
BYTE *bits = NULL;
void *buffer;
if (NULL == (buffer = (char*)malloc(width * height * PIXEL_SIZE)))
return (NULL);
set_bmi_object(&bmi, width, height);
hdc = GetDC(hwnd);
hDib = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, (void**)(&bits),
NULL, 0);
if (hDib != NULL) {
context_hdc = CreateCompatibleDC(hdc);
if (context_hdc == NULL) {
DeleteObject(hDib);
} else {
obj = SelectObject(context_hdc, hDib);
CopyMemory(bits, buffer, width * height * sizeof(PIXEL_SIZE));
}
}
return (newimg);
}
// Print the buffer of pixel on the window
void put_image_to_window(HWND hwnd, void *buffer, int x, int y)
{
(void)hwnd;
// Void buffer because i should use directly HDCcontext_hdc linked to HGDIOBJ obj ?
(void)buffer;
BitBlt(hdc, // destination
x,
y,
500, // width of the region
500, // height
context_hdc, // source
0, // x
0, // y
SRCCOPY);
UpdateWindow(hwnd);
}
static const char g_szClassName[] = "myWindowClass";
static void paint(HWND hwnd) {
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
EndPaint(hwnd, &ps);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
case WM_PAINT:
paint(hwnd);
return DefWindowProc(hwnd, msg, wParam, lParam);
}
int main(void) {
MSG Msg;
HINSTANCE hInstance;
HWND hwnd;
STARTUPINFOA startup_info;
WNDCLASSEX wc;
HWND hwnd;
GetStartupInfoA(&startup_info);
hInstance = GetModuleHandle(NULL);
memset(&wc, 0, sizeof(wc));
// Registering the Window Class
wc.cbSize = sizeof(WNDCLASSEX);
// ... etc
wc.lpszClassName = TEXT(g_szClassName);
if (!RegisterClassEx(&wc)) {
return (-1);
}
hwnd = CreateWindowEx(
WS_EX_CLIENTEDGE,
g_szClassName,
"Title,
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
CW_USEDEFAULT,
CW_USEDEFAULT,
500,
500,
NULL,
NULL,
hInstance,
NULL);
if (hwnd == NULL) {
return (-1);
}
ShowWindow(hwnd, startup_info.wShowWindow);
image = new_image(hwnd, 500, 500);
put_image_to_window(hwnd, image, 0, 0);
UpdateWindow(hwnd);
// The Message Loop
while (GetMessage(&Msg, NULL, 0, 0)) {
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return (Msg.wParam);
}
Here is in new_image.c
a function new_image that returns a pointer on a buffer of pixels,
a function put_image_to_window that display the buffer of pixels on the window.
Thanks to the answers from @RemyLebeau @IInspectable @Raymond Chen and @BarmakShemirani answers, here is a solution.
Now i successfully update the window according to buffer obtained with the CreateDIBSection() function, without passing through the WM_PAINT event.
I use the UpdateLayeredWindow() function to update the window's pixels.
Here is the solution code :
// global variables
static HBITMAP hDib;
static void set_bmi_object(BITMAPINFO *bmi, int width, int height) {
memset(bmi, 0, sizeof(BITMAPINFO));
bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi->bmiHeader.biWidth = width;
bmi->bmiHeader.biHeight = -height;
bmi->bmiHeader.biPlanes = 1;
bmi->bmiHeader.biBitCount = 32;
bmi->bmiHeader.biCompression = BI_RGB;
}
// Allocate a new image buffer
void *new_image(HWND hwnd, int width, int height)
{
BITMAPINFO bmi;
void *buffer;
HDC hdc;
set_bmi_object(&bmi, width, height);
hdc = GetDC(hwnd);
hDib = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, (void**)(&buffer), NULL, 0);
ReleaseDC(instance->win_list->hwnd, hdc);
return (buffer);
}
// Print the buffer of pixel on the window
void put_image_to_window(HWND hwnd, void *buffer, int x, int y)
{
HDC hdc;
HDC context_hdc;
HGDIOBJ old_obj;
hdc = GetDC(hwnd);
context_hdc = CreateCompatibleDC(hdc);
old_obj = SelectObject(context_hdc, hDib);
BitBlt(hdc,
0,
0,
500,
500,
context_hdc,
0,
0,
SRCCOPY);
SelectObject(context_hdc, old_obj);
DeleteDC(context_hdc);
ReleaseDC(hwnd, hdc);
// Call UpdateLayeredWindow
BLENDFUNCTION blend = {0};
blend.BlendOp = AC_SRC_OVER;
blend.SourceConstantAlpha = 128;// half transparent
blend.AlphaFormat = AC_SRC_ALPHA;
POINT ptLocation = {x, y};
SIZE szWnd = {500, 500};
POINT ptSrc = {0, 0};
UpdateLayeredWindow(hwnd, hdc, &ptLocation, &szWnd, context_hdc, &ptSrc, 0, &blend, ULW_ALPHA);
}
static const char g_szClassName[] = "myWindowClass";
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
int main(void) {
MSG Msg;
HINSTANCE hInstance;
HWND hwnd;
STARTUPINFOA startup_info;
WNDCLASSEX wc;
HWND hwnd;
GetStartupInfoA(&startup_info);
hInstance = GetModuleHandle(NULL);
memset(&wc, 0, sizeof(wc));
// Registering the Window Class
wc.cbSize = sizeof(WNDCLASSEX);
// ... etc
wc.lpszClassName = TEXT(g_szClassName);
if (!RegisterClassEx(&wc)) {
return (-1);
}
hwnd = CreateWindowEx(
WS_EX_CLIENTEDGE,
g_szClassName,
"Title,
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
CW_USEDEFAULT,
CW_USEDEFAULT,
500,
500,
NULL,
NULL,
hInstance,
NULL);
if (hwnd == NULL) {
return (-1);
}
ShowWindow(hwnd, startup_info.wShowWindow);
image = new_image(hwnd, 500, 500);
put_image_to_window(hwnd, image, 0, 0);
// The Message Loop
while (GetMessage(&Msg, NULL, 0, 0)) {
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return (Msg.wParam);
}
Here is a must read that @IInspectable gave, for WinAPI beginners like me : Painting and Drawing.
Should have read this before questionning ...