Bug in OpenGl_tXfm.c, function: loadTexFont

The MS Windows specific funtion loadTexFont in OpenGL_tXfm.c has a bug. It only occurs, when there are more than one occ-window for an application open.

Test case:
- 2 occ-windows (in one application) with an importet cad-model
- moving the modell constantly around with AIS_InteractiveContext.SetLocation and update the display with V3d_View.Redraw

What happens:
- for a short time everything works fine, but then there is suddenly a great slow-down from one redraw to an other
- the taskmanager of windows displays, that there is _much_ cpu-time for the kernel is used from this point on
- after a few minutes, the hole application crashs

The reason:
- the function loadTexFont in OpenGl_tXfm.c is called _very_ often
- windows ressources are created, but never freed (font, hDC, hBmp) so windows runs out of ressources

The main problem is, that loadTexFont is called so often when using multiple occ-windows. If font, hDC and hBmp is freed at the end of the function, the hole animation slows down to a constant lower frame rate, since much time is used by the kernel for creating and freeing the ressources.

Analyzing the function shows, that there are only two different fonts loaded. So there is now need to call the loadTexFont thousands of times. As a quick fix i added a statical list, that stores every loaded font, so that when loadTexFont is called the second time for a font, only the list has to be used. With this everything works.

Below is the changed function:

/*
* list to handle already loaded fonts
*/
struct font_cache_list {
struct font_cache_list *next;
char *font_name;
GLint tex_id;
};

static GLint loadTexFont(char* fontName, TM_FONT_HANDLE* fontHandle)
{
static struct font_cache_list *font_list = NULL;
struct font_cache_list *element = NULL;

GLint tex_id = -1;
HFONT font;
HDC hMemDC, hDC = NULL;
char str[2] = " ";
int i, j, l, num, code;
BITMAPINFO bi;
HBITMAP hBmp, hOldBmp;
const int spacing = 2; /* spacing between characters in a string */
GLubyte fontBits [256 * 256 * 3]; /* font bitmap array: RGB */
GLubyte ifontBits[256 * 256 * 2]; /* texture array: luminance and alpha */
int charWidths[MAX_NB_CHARS];

if (!fontHandle) {
return tex_id;
}

/*
* check if the font is already in the list
*/
element = font_list;
while (element != NULL && strcmp(fontName, element->font_name) != 0) {
element = element->next;
}
if (element != NULL) {
return element->tex_id;
}

memset(fontHandle, 0, sizeof(TM_FONT_HANDLE));

fontHandle->curRC = wglGetCurrentContext();
fontHandle->texSize = 256;
fontHandle->scale = 1.f;

/* draw the font glyphs on the square bitmap */
font = CreateFont(-16, /* Height Of Font*/
0, /* Width Of Font*/
0, /* Angle Of Escapement*/
0, /* Orientation Angle*/
FW_BOLD, /* Font Weight*/
FALSE, /* Italic*/
FALSE, /* Underline*/
FALSE, /* Strikeout*/
ANSI_CHARSET, /* Character Set Identifier*/
OUT_TT_PRECIS, /* Output Precision*/
CLIP_DEFAULT_PRECIS, /* Clipping Precision*/
NONANTIALIASED_QUALITY, /* Output Quality*/
FF_MODERN|DEFAULT_PITCH, /* Family And Pitch*/
fontName); /* Font Name*/

hDC = wglGetCurrentDC();
hMemDC = CreateCompatibleDC(hDC);
hBmp = CreateCompatibleBitmap(hDC, fontHandle->texSize, fontHandle->texSize);
hOldBmp = (HBITMAP)SelectObject(hMemDC, hBmp);
SelectObject(hMemDC, font);
SetTextColor(hMemDC, RGB(255, 255, 255));
SetBkColor (hMemDC, RGB(0, 0, 0));
GetCharWidth32(hDC, 0, MAX_NB_CHARS - 1, charWidths);

for (i = 0; i for (j = 0; j code = i * 16 + j;
str[0] = (char)code;
l = strlen(str);
TextOut(hMemDC, j * CHAR_SIZE, i * CHAR_SIZE, str, l);
/* calculate advance ratio for each character */
fontHandle->charRatios[code] = (float) (charWidths[code] + spacing) / (float) CHAR_SIZE;
}
}

/* retrieve the font bitmap */
memset(&bi, 0, sizeof(BITMAPINFOHEADER));
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bi.bmiHeader.biPlanes = 1;
bi.bmiHeader.biBitCount = 24;
bi.bmiHeader.biHeight = -fontHandle->texSize;
bi.bmiHeader.biWidth = fontHandle->texSize;
bi.bmiHeader.biCompression = BI_RGB;
SelectObject(hMemDC, hOldBmp);
num = GetDIBits(hMemDC, hBmp, 0, fontHandle->texSize, fontBits, &bi, DIB_RGB_COLORS);

/* prepare an array of alpha and luminance values */
for (i = 0; i texSize; i++) {
for(j = 0; j texSize; j++) {
ifontBits[(i * fontHandle->texSize + j) * 2] = fontBits[(i * fontHandle->texSize + j) * 3];
ifontBits[(i * fontHandle->texSize + j) * 2 + 1] = fontBits[(i * fontHandle->texSize + j) * 3];
}
}

/* create the font texture */
glGenTextures(1, &tex_id);
glBindTexture(GL_TEXTURE_2D, tex_id);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_NEAREST);

glTexImage2D(GL_TEXTURE_2D,
0,
GL_INTENSITY,
fontHandle->texSize,
fontHandle->texSize,
0,
GL_LUMINANCE_ALPHA,
GL_UNSIGNED_BYTE,
ifontBits);

fontHandle->textureId = tex_id;

/*
* add the new font to the list
*/
element = (struct font_cache_list *) malloc(sizeof(struct font_cache_list));
element->next = NULL;
element->font_name = fontName;
element->tex_id = tex_id;
if (font_list == NULL) {
font_list = element;
} else {
struct font_cache_list *last_element = font_list;
while (last_element->next != NULL) {
last_element = last_element->next;
}
last_element->next = element;
}

/*
* free windows ressources
*/
DeleteObject(font);
DeleteObject(hBmp);
DeleteDC(hMemDC);

return tex_id;
}