Rendering OpenGL canvas within a WC_TABCONTROL - c++

Question

My goal is to create a basic tab control using the Win32 API that contains a canvas for rendering OpenGL. My tab contains a static control for rendering OpenGL. However, the only way I can get the canvas to appear in the GUI is to exclude the tab control (comment out the CREATE_TAB_PANE macro in my example to do this).
My example is given below:
// OpenGlTabWin32.cpp
// NOTE: canvas displays fine if TabPane creation is commented out
#include <windows.h>
#include <commctrl.h>
#include <gl/GL.h>
#pragma comment(linker, "\"/manifestdependency:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
#pragma comment(lib, "comctl32.lib")
#pragma comment(lib, "opengl32.lib")
#define CREATE_TAB_PANE
enum { IDC_TAB = 200, IDC_CANVAS = 201 };
static HWND TabPaneId;
static HWND CanvasId;
static WNDPROC CanvasWndProc;
static HGLRC CanvasRc;
static HDC CanvasDc;
////////////////////////////////////////////////////////////////////////////////
// WndProc
////////////////////////////////////////////////////////////////////////////////
static LRESULT CALLBACK WndProc(HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam) {
switch (msg) {
case WM_CREATE:
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
////////////////////////////////////////////////////////////////////////////////
// OpenGlCanvasProc
////////////////////////////////////////////////////////////////////////////////
static LRESULT CALLBACK OpenGlCanvasProc(HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam) {
if (msg == WM_PAINT) {
PAINTSTRUCT ps;
BeginPaint(hwnd, &ps);
EndPaint(hwnd, &ps);
wglMakeCurrent(CanvasDc, CanvasRc);
SwapBuffers(CanvasDc);
return 0;
}
return CallWindowProc(CanvasWndProc, hwnd, msg, wParam, lParam);
}
////////////////////////////////////////////////////////////////////////////////
// CanvasInit
////////////////////////////////////////////////////////////////////////////////
static void CanvasInit() {
glClearColor(0.0, 0.0, 0.0, 0.0);
}
////////////////////////////////////////////////////////////////////////////////
// CanvasResize
////////////////////////////////////////////////////////////////////////////////
static void CanvasResize(int width, int height) {
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 1, 0, 1, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
////////////////////////////////////////////////////////////////////////////////
// CanvasDisplay
////////////////////////////////////////////////////////////////////////////////
static void CanvasDisplay() {
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glColor3d(1, 0, 0);
glBegin(GL_LINE_STRIP);
glVertex2d(0.2, 0.2);
glVertex2d(0.8, 0.8);
glEnd();
SwapBuffers(CanvasDc);
}
////////////////////////////////////////////////////////////////////////////////
// WinMain
////////////////////////////////////////////////////////////////////////////////
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nShowCmd) {
// Create window
const char *className = "OpenGlTab";
WNDCLASSEX wc;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = className;
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if (!RegisterClassEx(&wc)) {
exit(0);
}
HWND winId = CreateWindowEx(0,
className,
"Tab Pane w/ OpenGL",
WS_OVERLAPPEDWINDOW,
100, 100, 600, 400,
0,
0,
hInstance,
0);
if (!winId) {
exit(0);
}
ShowWindow(winId, nShowCmd);
UpdateWindow(winId);
#ifdef CREATE_TAB_PANE
// Create tab pane
TabPaneId = CreateWindow(WC_TABCONTROL,
0,
WS_CHILD | WS_VISIBLE,
10, 10, 566, 343,
winId,
HMENU(IDC_TAB),
hInstance,
0);
TCITEM tabItem = {0};
tabItem.mask = TCIF_TEXT;
tabItem.pszText = "Tab";
SendMessage(TabPaneId, TCM_INSERTITEM, 0, LPARAM(&tabItem));
#endif
// Create OpenGL canvas
int w = 200;
int h = 200;
CanvasId = CreateWindow("static",
"",
WS_CHILD | WS_VISIBLE | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
20, 100, w, h,
winId,
HMENU(IDC_CANVAS),
hInstance,
0);
CanvasWndProc = (WNDPROC)SetWindowLongPtr(CanvasId,
GWLP_WNDPROC,
(LONG_PTR)OpenGlCanvasProc);
CanvasDc = GetDC(CanvasId);
static PIXELFORMATDESCRIPTOR pfd = {
sizeof(PIXELFORMATDESCRIPTOR),
1, // version
PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
32, // color depth
0, 0, 0, 0, 0, 0,
0, 0,
0, 0, 0, 0, 0,
16, // depth buffer
0,
0,
0,
0,
0, 0, 0
};
int pixelFormat = ChoosePixelFormat(CanvasDc, &pfd);
SetPixelFormat(CanvasDc, pixelFormat, &pfd);
CanvasRc = wglCreateContext(CanvasDc);
// Render OpenGL canvas
wglMakeCurrent(CanvasDc, CanvasRc);
CanvasResize(w, h);
CanvasInit();
CanvasDisplay();
SwapBuffers(CanvasDc);
// Execute GUI
MSG msg;
while (GetMessage(&msg, 0, 0, 0) > 0) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}
My updated example with changes per Chris:
// OpenGlTabWin32.cpp
// NOTE: canvas displays fine if TabPane creation is commented out
#include <windows.h>
#include <commctrl.h>
#include <gl/GL.h>
#pragma comment(linker, "\"/manifestdependency:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
#pragma comment(lib, "comctl32.lib")
#pragma comment(lib, "opengl32.lib")
#define CREATE_TAB_PANE
enum { IDC_TAB = 200, IDC_CANVAS = 201 };
static HWND TabPaneId;
static HWND CanvasId;
static WNDPROC CanvasWndProc;
static HGLRC CanvasRc;
////////////////////////////////////////////////////////////////////////////////
// WndProc
////////////////////////////////////////////////////////////////////////////////
static LRESULT CALLBACK WndProc(HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam) {
switch (msg) {
case WM_CREATE:
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
////////////////////////////////////////////////////////////////////////////////
// CanvasInit
////////////////////////////////////////////////////////////////////////////////
static void CanvasInit() {
glClearColor(0.0, 0.0, 0.0, 0.0);
}
////////////////////////////////////////////////////////////////////////////////
// CanvasResize
////////////////////////////////////////////////////////////////////////////////
static void CanvasResize(int width, int height) {
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 1, 0, 1, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
////////////////////////////////////////////////////////////////////////////////
// CanvasDisplay
////////////////////////////////////////////////////////////////////////////////
static void CanvasDisplay() {
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glColor3d(1, 0, 0);
glBegin(GL_LINE_STRIP);
glVertex2d(0.2, 0.2);
glVertex2d(0.8, 0.8);
glEnd();
}
////////////////////////////////////////////////////////////////////////////////
// OpenGlCanvasProc
////////////////////////////////////////////////////////////////////////////////
static LRESULT CALLBACK OpenGlCanvasProc(HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam) {
switch (msg) {
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
wglMakeCurrent(hdc, CanvasRc);
CanvasDisplay();
SwapBuffers(hdc);
wglMakeCurrent(NULL, NULL);
ReleaseDC(hwnd, hdc);
EndPaint(hwnd, &ps);
return 0;
}
case WM_SIZE:
{
HDC hdc = GetDC(hwnd);
wglMakeCurrent(hdc, CanvasRc);
CanvasResize(LOWORD(lParam), HIWORD(lParam));
wglMakeCurrent(NULL, NULL);
ReleaseDC(hwnd, hdc);
return 0;
}
}
return CallWindowProc(CanvasWndProc, hwnd, msg, wParam, lParam);
}
////////////////////////////////////////////////////////////////////////////////
// WinMain
////////////////////////////////////////////////////////////////////////////////
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nShowCmd) {
// Create window
const char *className = "OpenGlTab";
WNDCLASSEX wc;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);
wc.lpszMenuName = NULL;
wc.lpszClassName = className;
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if (!RegisterClassEx(&wc)) {
exit(0);
}
HWND winId = CreateWindowEx(0,
className,
"Tab Pane w/ OpenGL",
WS_OVERLAPPEDWINDOW,
100, 100, 600, 400,
0,
0,
hInstance,
0);
if (!winId) {
exit(0);
}
ShowWindow(winId, nShowCmd);
UpdateWindow(winId);
#ifdef CREATE_TAB_PANE
// Create tab pane
TabPaneId = CreateWindow(WC_TABCONTROL,
0,
WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS,
10, 10, 566, 343,
winId,
HMENU(IDC_TAB),
hInstance,
0);
TCITEM tabItem = {0};
tabItem.mask = TCIF_TEXT;
tabItem.pszText = "Tab";
SendMessage(TabPaneId, TCM_INSERTITEM, 0, LPARAM(&tabItem));
#endif
// Create OpenGL canvas
int w = 200;
int h = 200;
CanvasId = CreateWindow("static",
"",
WS_CHILD | WS_VISIBLE | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
20, 100, w, h,
winId,
HMENU(IDC_CANVAS),
hInstance,
0);
CanvasWndProc = (WNDPROC)SetWindowLongPtr(CanvasId,
GWLP_WNDPROC,
(LONG_PTR)OpenGlCanvasProc);
HDC hdc = GetDC(CanvasId);
static PIXELFORMATDESCRIPTOR pfd = {
sizeof(PIXELFORMATDESCRIPTOR),
1, // version
PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
32, // color depth
0, 0, 0, 0, 0, 0,
0, 0,
0, 0, 0, 0, 0,
16, // depth buffer
0,
0,
0,
0,
0, 0, 0
};
int pixelFormat = ChoosePixelFormat(hdc, &pfd);
SetPixelFormat(hdc, pixelFormat, &pfd);
CanvasRc = wglCreateContext(hdc);
// Render OpenGL canvas
wglMakeCurrent(hdc, CanvasRc);
CanvasResize(w, h);
CanvasInit();
CanvasDisplay();
SwapBuffers(hdc);
wglMakeCurrent(NULL, NULL);
ReleaseDC(CanvasId, hdc);
// Execute GUI
MSG msg;
while (GetMessage(&msg, 0, 0, 0) > 0) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}

Answer 1

You have a number of things going on in this sample that are all possibly contributing:
The most immediate issue might simply be that the tab window is covering the canvas window and you are not actually painting anything in response to WM_PAINT. The tab control is going to paint over your canvas as soon as its invalidated as Windows usually lets child windows paint all over each other; so adding WS_CLIPSIBLINGS to the tab control might help.
You are grabbing an HDC to the static control and holding on to it after associating it with the current wgl context. You should not really do this unless you are using a window class with CS_OWNDC and especially not with one that probably has CS_PARENTDC (because then, as soon as the parent - or a different child - window paints, the DC is re-associated with a window that never had SetPixelFormat associated with it).
You are just making your opengl context current, and expecting it to be set later. This is fine - assuming you have a CS_OWNDC window with an HDC you can grab up front and keep around - and also assuming you never want to create a 2nd GL context for any reason.
So, when doing OpenGL in an application where you are not controlling the window class styles (or there might be more than one OpenGL context) you need to ensure that you always clear the current context and release the DC as soon as you are done with it.
For example, your CanvasWindowProc should look more like this:
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd,&ps);
wglMakeCurrent(glrc,hdc);
CanvasDisplay();
SwapBuffers();
wglMakeCurrent(NULL,NULL);
EndPaint(&ps);
}
return 0;
case WM_SIZE:
{
HDC hdc = GetDC(hwnd);
wglMakeCurrent(glrc,hdc);
CanvasResize(LOWORD(lParam),HIWORD(lParam));
wglMakeCurrent(NULL,NULL);
ReleaseDC(hwnd,hdc);
}
break;