OpenGL Screensaver Preview Window

EDN Admin · Aug 7, 2012

Hi everyone. Ive been having trouble getting anything to show up in the preview window of my OpenGL screensaver. Just to make sure Ive got this problem solved before moving on to actually making a miniature version of my screensaver Ive been 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 other
screensaver to when it actually switches over the preview window does turn white. I suspect something like a redisplay is needed but InvalidateRect didnt do the trick. Heres my code. 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 could be going wrong?

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OpenGL Screensaver Preview Window

EDN Admin

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