OpenGL Screensaver Preview Window

EDN Admin · Aug 7, 2012

Hi everyone. Ive been struggling sometime now to get my OpenGL windows screensaver to display a preview in the preview window. Just to make sure Ive cleared that hurdle before moving on to actually making a miniature version draw itself in the preview
window Im trying to get a white texture to show up in the preview window. It isnt working. When I select my screensaver the preview window remains black. However, I have noticed that when I go to select a different screensaver for a split second from when
I select the new screensaver to when it actually changes over the preview window does turn white. I suspect something like a redisplay command is needed but InvalidateRect isnt doing the trick. Ill post my code here. WARNING! Its long.

#include <windows.h> 
#include <scrnsave.h> 
#include <GL/glu.h> 
#include <GL/gl.h> 
#include <stdlib.h> 
#include <math.h> 
#include <time.h> 
#include "resource.h" 
 
#pragma comment(lib, "OpenGL32.lib") 
#pragma comment(lib, "GLu32.lib") 
 
 
#ifdef UNICODE 
 
#pragma comment(lib, "ScrnSavw.lib") 
 
#else 
 
#pragma comment(lib, "ScrnSave.lib") 
 
#endif 
 
 
 
#pragma comment(lib, "comctl32.lib") 
 
//get rid of these warnings: 
//truncation from const double to float 
//conversion from double to float 
#pragma warning(disable: 4305 4244) 
 
//Define a Windows timer 
 
#define TIMER 1 
 
struct PIXELA 
{ 
GLubyte r, g, b, a; 
}; 
 
bool previewMode = false; 
 
int sphereDiameter; 
float mag = 1.0f; 
 
float **offsetX1, **offsetY1, **offsetX2, **offsetY2; 
float **offsetX3, **offsetY3, **offsetX4, **offsetY4; 
 
PIXELA *thetex; 
 
GLubyte *pixelBuffer; 
 
GLuint textureId, tex; 
 
int Width, Height; 
 
int xpos, ypos, step = 6; 
bool goRight = true, goUp = true; 
 
bool inChild = false; 
 
void InitGL(HWND hWnd, HDC & hDC, HGLRC & hRC); 
void CloseGL(HWND hWnd, HDC hDC, HGLRC hRC); 
void SetupAnimation(int Width, int Height); 
void OnTimer(HDC hDC); 
 
// Screen Saver Procedure 
LRESULT WINAPI ScreenSaverProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) 
{ 
static HDC hDC; 
static HGLRC hRC; 
static RECT rect; 
LPWSTR lpCmdLine; 
char cmdLine[40] = {0}; 
HWND parentWnd; 
int i; 
 
switch(message) 
{ 
 
case WM_CREATE: 
lpCmdLine = GetCommandLine(); 
 
wcstombs(cmdLine, lpCmdLine, 40); 
 
for(i = 0;i < 30;i++) 
{ 
if(cmdLine == / && cmdLine[i + 1] == p) 
{ 
previewMode = true; 
break; 
} 
} 
 
if(previewMode && !inChild) 
{ 
parentWnd = (HWND)atoi(&cmdLine[i + 3]); 
 
GetClientRect(parentWnd, &rect); 
 
Width = rect.right - rect.left; 
Height = rect.bottom - rect.top; 
 
LPCTSTR lpszClassName = TEXT("LensEffectScreenSaver"); 
 
WNDCLASSEX wc; 

ZeroMemory(&wc, sizeof(wc)); 
wc.cbSize
wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC; 
wc.lpfnWndProc = (WNDPROC) ScreenSaverProc; 
wc.cbClsExtra
wc.cbWndExtra = 0; 
wc.hInstance = (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE); 
wc.hIcon = NULL; 
wc.hCursor = LoadCursor(NULL, IDC_ARROW); 
wc.hbrBackground = NULL; 
wc.lpszMenuName = NULL; 
wc.lpszClassName = lpszClassName; 
 
RegisterClassEx(&wc); 
 
inChild = true; 
 
hWnd = CreateWindowEx(NULL, lpszClassName, TEXT(""), WS_VISIBLE | WS_CHILD | WS_CLIPCHILDREN, 0, 0, Width, Height, parentWnd, NULL, (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE), NULL); 
 
SetWindowPos(hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE); 
ShowWindow(hWnd, SW_SHOW); 
UpdateWindow(hWnd); 
SetFocus(hWnd); 
 
sphereDiameter = (int)(0.29296875 * Width); 
 
if(sphereDiameter % 2 != 0) 
sphereDiameter++; 
 
xpos = -1 * sphereDiameter / 2; 
ypos = -1 * sphereDiameter / 2; 
 
 
// setup OpenGL, then animation 
InitGL(hWnd, hDC, hRC); 
 
SetupAnimation(Width, Height); 
 
//set timer to tick every 10 ms 
SetTimer(hWnd, TIMER, 10, NULL); 
} 
else if(!previewMode) 
{ 
GetClientRect(hWnd, &rect); 
 
Width = rect.right; 
Height = rect.bottom; 
 
sphereDiameter = (int)(0.29296875 * Width); 
 
if(sphereDiameter % 2 != 0) 
sphereDiameter++; 
 
xpos = -1 * sphereDiameter / 2; 
ypos = -1 * sphereDiameter / 2; 
 
 
// setup OpenGL, then animation 
InitGL(hWnd, hDC, hRC); 
 
SetupAnimation(Width, Height); 
 
//set timer to tick every 10 ms 
SetTimer(hWnd, TIMER, 10, NULL); 
} 
 
return 0; 
 
case WM_DESTROY: 
 
KillTimer(hWnd, TIMER); 
CloseGL(hWnd, hDC, hRC); 
 
return 0; 
 
case WM_TIMER: 
 
OnTimer(hDC); //animate! 
 
return 0; 
 
} 
 
return DefScreenSaverProc(hWnd, message, wParam, lParam); 
 
} 
 
BOOL WINAPI ScreenSaverConfigureDialog(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) 
{ 
 
// Dialog message handling 
switch(message) 
{ 
case WM_COMMAND: 
switch(LOWORD(wParam)) 
{ 
case IDOK: 
EndDialog(hDlg, LOWORD(wParam) == IDOK); 
return true; 
 
case IDCANCEL: 
EndDialog(hDlg, LOWORD(wParam) == IDOK); 
return true; 
} 
} 
 
return false; 
} 
 
 
 
// needed for SCRNSAVE.LIB 
BOOL WINAPI RegisterDialogClasses(HANDLE hInst) 
{ 
return TRUE; 
} 
 
void transform(float i, float j, float *ix, float *iy) 
{ 
float x, y, xnew, ynew; 
float r, theta, rnew, thetanew; 
 
x = i / ((float)sphereDiameter / 2.0f) - 1.0f; 
y = j / ((float)sphereDiameter / 2.0f) - 1.0f; 
 
r = sqrtf(x * x + y * y); 
 
theta = atan2f(y, x); 
 
rnew = asinf(r) / 1.5707963f; 
 
thetanew = theta; 
xnew = rnew * cos(thetanew) * mag; 
ynew = rnew * sin(thetanew) * mag; 
 
if(rnew <= r) 
{ 
*ix = (xnew + 1.0f) / 2.0f; 
*iy = (ynew + 1.0f) / 2.0f; 
} 
else 
{ 
*ix = (x + 1.0f) / 2.0f; 
*iy = (y + 1.0f) / 2.0f; 
} 
} 
 
// Initialize OpenGL 
static void InitGL(HWND hWnd, HDC & hDC, HGLRC & hRC) 
{ 
static PIXELFORMATDESCRIPTOR pfd = 
{ 
sizeof(PIXELFORMATDESCRIPTOR), 
1, // nVersion should be set to 1 
PFD_DRAW_TO_WINDOW | // buffer can draw to window 
PFD_SUPPORT_OPENGL | // buffer supports OpenGL drawing 
PFD_DOUBLEBUFFER, // buffer is double buffered 
PFD_TYPE_RGBA, // rgba pixels 
32, // 32-bit color depth 
0, 0, 0, 0, 0, 0, // look up rest at MSDN, color bits ignored 
0, // no alpha buffer 
0, // shift bit ignored 
0, // no accumulation buffer 
0, 0, 0, 0, // accumulation bits 
16, // 16 bit z buffer 
0, // no stencil buffer 
0, // no auxiliary buffer 
PFD_MAIN_PLANE, // main drawing layer 
0, // reserved 
0, 0, 0 // layer mask ignored 
}; 
 
if(!previewMode) 
{ 
hDC = GetDC(hWnd); 
 
int pf = ChoosePixelFormat(hDC, &pfd); 
SetPixelFormat(hDC, pf, &pfd); 
 
hRC = wglCreateContext(hDC); 
wglMakeCurrent(hDC, hRC); 
 
pixelBuffer = new GLubyte[sizeof(GLubyte) * Width * Height * 4]; 
 
glReadBuffer(GL_FRONT); 

GLint ReadBuffer; 
glGetIntegerv(GL_READ_BUFFER, &ReadBuffer); 
glPixelStorei(GL_READ_BUFFER, GL_RGBA); 

GLint PackAlignment; 
glGetIntegerv(GL_PACK_ALIGNMENT, &PackAlignment); 
glPixelStorei(GL_PACK_ALIGNMENT, 1); 

glReadPixels(0, 0, Width, Height, GL_RGBA, GL_UNSIGNED_BYTE, pixelBuffer); 
 
thetex = (PIXELA *)malloc(sphereDiameter * sphereDiameter * sizeof(PIXELA)); 
} 
else 
{ 
hDC = GetDC(hWnd); 
 
if(!hDC) 
MessageBox(NULL, TEXT("Bad device context"), TEXT("Bad hDC"), MB_OK); 
 
int pf = ChoosePixelFormat(hDC, &pfd); 
SetPixelFormat(hDC, pf, &pfd); 
 
hRC = wglCreateContext(hDC); 
 
if(!hRC) 
MessageBox(NULL, TEXT("Bad rendering context"), TEXT("Bad hRC"), MB_OK); 
 
wglMakeCurrent(hDC, hRC); 
 
pixelBuffer = new GLubyte[sizeof(GLubyte) * Width * Height * 4]; 
 
for(int i = 0;i < Width * Height * 4;i++) 
pixelBuffer = (GLubyte)255; 
} 
 
offsetX1 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetX1 = new float[sphereDiameter]; 
 
offsetX2 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetX2 = new float[sphereDiameter]; 
 
offsetX3 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetX3 = new float[sphereDiameter]; 
 
offsetX4 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetX4 = new float[sphereDiameter]; 
 
offsetY1 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetY1 = new float[sphereDiameter]; 
 
offsetY2 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetY2 = new float[sphereDiameter]; 
 
offsetY3 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetY3 = new float[sphereDiameter]; 
 
offsetY4 = new float*[sphereDiameter]; 
 
for(int i = 0; i < sphereDiameter; i++) 
offsetY4 = new float[sphereDiameter]; 
} 
 
// Shut down OpenGL 
static void CloseGL(HWND hWnd, HDC hDC, HGLRC hRC) 
{ 
wglMakeCurrent(NULL, NULL); 
wglDeleteContext(hRC); 
 
ReleaseDC(hWnd, hDC); 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetX1; 
 
delete offsetX1; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetX2; 
 
delete offsetX2; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetX3; 
 
delete offsetX3; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetX4; 
 
delete offsetX4; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetY1; 
 
delete offsetY1; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetY2; 
 
delete offsetY2; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetY3; 
 
delete offsetY3; 
 
for(int i = 0; i < sphereDiameter; i++) 
delete offsetY4; 
 
delete offsetY4; 
 
if(!previewMode) 
free(thetex); 
 
delete pixelBuffer; 
} 
 
void SetupAnimation(int Width, int Height) 
{ 
//window resizing stuff 
glViewport(0, 0, (GLsizei)Width, (GLsizei)Height); 
 
glMatrixMode(GL_PROJECTION); 
glLoadIdentity(); 
 
gluPerspective(45.0, (double)Width / (double)Height, 1.0, 200.0); 
 
glMatrixMode(GL_MODELVIEW); 
 
glLoadIdentity(); 
 
//background 
//glClearColor(0.0, 0.0, 0.0, 0.0); //0.0s is black 
 
glShadeModel(GL_SMOOTH); 
 
float i, j; 
int p, q; 
 
for(i = 0.0f, p = 0;i < (float)sphereDiameter;i += 1.0f, p++) 
{ 
for(j = 0.0f, q = 0;j < (float)sphereDiameter;j += 1.0f, q++) 
{ 
transform(i, j, &offsetX1[p][q], &offsetY1[p][q]); 
transform(i, j + 1.0f, &offsetX2[p][q], &offsetY2[p][q]); 
transform(i + 1.0f, j, &offsetX3[p][q], &offsetY3[p][q]); 
transform(i + 1.0f, j + 1.0f, &offsetX4[p][q], &offsetY4[p][q]); 
} 
} 
} 
 
void OnTimer(HDC hDC) 
{ 
float x, y, i = 0.0f, j = 0.0f; 
int a, b, Y; 
 
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
 
glLoadIdentity(); 
 
glDepthMask(GL_FALSE); 
 
glGenTextures(1, &textureId); 
glBindTexture(GL_TEXTURE_2D, textureId); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP); 
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); 
 
glTexImage2D(GL_TEXTURE_2D, 0, 4, Width, Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixelBuffer); 
 
glMatrixMode(GL_PROJECTION); 
glLoadIdentity(); 
gluPerspective(180.0, (float)Width / (float)Height, 0.1, 10000.0); 
glMatrixMode(GL_MODELVIEW); 
glLoadIdentity(); 
 
gluLookAt(70, 0, 0, 0, 0, 0, 0, 1, 0); 
 
glEnable(GL_TEXTURE_2D); 
 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); 
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); 
 
glMatrixMode(GL_PROJECTION); 
glLoadIdentity(); 
glOrtho(-1 * Width / 2, Width / 2, -1 * Height / 2, Height / 2, 1.0, 10000.0); 
glMatrixMode(GL_MODELVIEW); 
glLoadIdentity(); 
gluLookAt(0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0); 
glNormal3f(0.0, 0.0, 1.0); 
 
glBegin(GL_TRIANGLE_STRIP); 
 
glTexCoord2f(0.0f, 0.0f); 
glVertex3f(-1.0f * (float)Width / 2.0f, -1.0f * (float)Height / 2.0f, 0.0f); 
glTexCoord2f(0.0f, 1.0f); 
glVertex3f(-1.0f * (float)Width / 2.0f, (float)Height / 2.0f, 0.0f); 
glTexCoord2f(1.0f, 0.0f); 
glVertex3f((float)Width / 2.0f, -1.0f * (float)Height / 2.0f, 0.0f); 
glTexCoord2f(1.0f, 1.0f); 
glVertex3f((float)Width / 2.0f, (float)Height / 2.0f, 0.0f); 
 
glEnd(); 
 
glDisable(GL_TEXTURE_2D); 
 
glDeleteTextures(1, &textureId); 
 
if(!previewMode) 
{ 
Y = ypos; 
 
b = (((Height / 2 + Y) * Width) * 4) + (((Width / 2) + xpos) * 4); 
 
for(a = 0;a < sphereDiameter * sphereDiameter;a++, b += 4) 
{ 
if(a % 300 == 0 && a != 0) 
{ 
Y++; 
b = (((Height / 2 + Y) * Width) * 4) + (((Width / 2) + xpos) * 4); 
} 
 
thetex[a].r = pixelBuffer; 
thetex[a].g = pixelBuffer[b + 1]; 
thetex[a].b = pixelBuffer[b + 2]; 
thetex[a].a = pixelBuffer[b + 3]; 
} 
 
glGenTextures(1, &tex); 
glBindTexture(GL_TEXTURE_2D, tex); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP); 
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP); 
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); 
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); 
glTexImage2D(GL_TEXTURE_2D, 0, 4, sphereDiameter, sphereDiameter, 0, GL_RGBA, GL_UNSIGNED_BYTE, thetex); 
 
glEnable(GL_TEXTURE_2D); 
glBindTexture(GL_TEXTURE_2D, tex); 
 
glBegin(GL_TRIANGLE_STRIP); 
 
glTexCoord2f(offsetX1[(int)i][(int)j], offsetY1[(int)i][(int)j]); 
glVertex3f((float)xpos, (float)ypos, 0.0f); 
glTexCoord2f(offsetX2[(int)i][(int)j], offsetY2[(int)i][(int)j]); 
glVertex3f(i + (float)xpos, (j + 1.0f) + (float)ypos, 0.0f); 
glTexCoord2f(offsetX3[(int)i][(int)j], offsetY3[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, j + (float)ypos, 0.0f); 
glTexCoord2f(offsetX4[(int)i][(int)j], offsetY4[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, (j + 1.0f) + (float)ypos, 0.0f); 
 
while(true) 
{ 
i += 1.0f; 
 
if(i == (float)sphereDiameter) 
{ 
glEnd(); 
 
j += 1.0f; 
 
if(i == (float)sphereDiameter && j == (float)sphereDiameter) 
break; 
 
i = 0.0f; 
 
glBegin(GL_TRIANGLE_STRIP); 
 
glTexCoord2f(offsetX1[(int)i][(int)j], offsetY1[(int)i][(int)j]); 
glVertex3f((float)xpos, (float)ypos, 0.0f); 
glTexCoord2f(offsetX2[(int)i][(int)j], offsetY2[(int)i][(int)j]); 
glVertex3f(i + (float)xpos, (j + 1.0f) + (float)ypos, 0.0f); 
glTexCoord2f(offsetX3[(int)i][(int)j], offsetY3[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, j + (float)ypos, 0.0f); 
glTexCoord2f(offsetX4[(int)i][(int)j], offsetY4[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, (j + 1.0f) + (float)ypos, 0.0f); 
 
//i += 1.0f; 
} 
 
glTexCoord2f(offsetX3[(int)i][(int)j], offsetY3[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, j + (float)ypos, 0.0f); 
glTexCoord2f(offsetX4[(int)i][(int)j], offsetY4[(int)i][(int)j]); 
glVertex3f((i + 1.0f) + (float)xpos, (j + 1.0f) + (float)ypos, 0.0f); 
} 
 
 
glBegin(GL_QUADS); 
transform(0.0f, 0.0f, &x, &y); 
glTexCoord2f(x, y); 
glVertex3f((float)xpos, (float)ypos, 0.0f); 
transform(1.0f, 0.0f + 4.0f, &x, &y); 
glTexCoord2f(x, y); 
glVertex3f(1.0f + (float)xpos, (float)ypos, 0.0f); 
transform(1.0f, (float)sphereDiameter, &x, &y); 
glTexCoord2f(x, y); 
glVertex3f(1.0f + (float)xpos, (float)sphereDiameter + (float)ypos, 0.0f); 
transform(0.0f, (float)sphereDiameter, &x, &y); 
glTexCoord2f(x, y); 
glVertex3f((float)xpos, (float)sphereDiameter + (float)ypos, 0.0f); 
glEnd(); 
 
glDisable(GL_TEXTURE_2D); 
} 
 
glFlush(); 
 
hDC = wglGetCurrentDC(); 
 
SwapBuffers(hDC); 
 
if(!previewMode) 
glDeleteTextures(1, &tex); 
 
if(xpos >= Width / 2 - (sphereDiameter + step)) 
goRight = false; 
else if(xpos <= -1 * Width / 2 + step) 
goRight = true; 
 
if(ypos >= Height / 2 - (sphereDiameter + step)) 
goUp = false; 
else if(ypos <= -1 * Height / 2 + step) 
goUp = true; 
 
if(goRight) 
xpos += step; 
else 
xpos -= step; 
 
if(goUp) 
ypos += step; 
else 
ypos -= step; 
}

Any ideas where I might be going wrong?

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OpenGL Screensaver Preview Window

EDN Admin

Well-known member

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