Elie at 13:40, 30 November 2022

2022-11-30T13:40:24Z

← Older revision		Revision as of 09:40, 30 November 2022
Line 1:		Line 1:
	~~Dependency~~: [[:File:font.data-uint8-1004x19]]		C header for drawing text in OpenGL.
			Depends on font bitmap: [[:File:font.data-uint8-1004x19]]

	==Code==		==Code==

Elie at 13:37, 30 November 2022

2022-11-30T13:37:48Z

← Older revision		Revision as of 09:37, 30 November 2022
Line 1:		Line 1:
			Dependency: [[:File:font.data-uint8-1004x19]]

			==Code==
	<syntaxhighlight lang="c">		<syntaxhighlight lang="c">
	// text-quads.h		// text-quads.h

Elie: Created page with " // text-quads.h // Functions for drawing text in OpenGL, using textured quads. #define TQ_TEXTURE_WIDTH 1004 #define TQ_TEXTURE_HEIGHT 19 #define TQ_TEXTURE_FILENAME "font.data-uint8-1004x19" // DEPENDENCY: This texture file. /* Copyright 2022, Elie Goldman Smith This program is FREE SOFTWARE: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either ver..."

2022-11-30T13:36:34Z

Created page with "<syntaxhighlight lang="c"> // text-quads.h // Functions for drawing text in OpenGL, using textured quads. #define TQ_TEXTURE_WIDTH 1004 #define TQ_TEXTURE_HEIGHT 19 #define TQ_TEXTURE_FILENAME "font.data-uint8-1004x19" // DEPENDENCY: This texture file. /* Copyright 2022, Elie Goldman Smith This program is FREE SOFTWARE: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either ver..."

New page

<syntaxhighlight lang="c">
// text-quads.h
// Functions for drawing text in OpenGL, using textured quads.
#define TQ_TEXTURE_WIDTH 1004
#define TQ_TEXTURE_HEIGHT 19
#define TQ_TEXTURE_FILENAME "font.data-uint8-1004x19" // DEPENDENCY: This texture file.

/*
Copyright 2022, Elie Goldman Smith

This program is FREE SOFTWARE: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/

#include <string.h>
typedef struct { float x, y, tx, ty; } TQ_Vertex; // XXX: maybe use 16-bit snorm instead of 32-bit float?
typedef struct { TQ_Vertex *v; int n; int isComplete;} TQ_Drawable;// XXX: in future versions, isComplete might get renamed to 'flags'
TQ_Vertex _tq_alphabet[1024]; // 256 quads (one for every char value)
GLuint _tq_texture;

void tq_init() {
// load font bitmap
size_t SIZE = TQ_TEXTURE_WIDTH*TQ_TEXTURE_HEIGHT;
unsigned char *bitmap = malloc(SIZE);
if (!bitmap) return; // TODO: handle error better
FILE *f = fopen(TQ_TEXTURE_FILENAME,"r");
if (!f) { perror(TQ_TEXTURE_FILENAME); return; } // TODO: handle error better
int n = fread(bitmap, 1, SIZE, f);
if (n != SIZE) { printf("read %d chars\n", n); fclose(f); return; } // TODO: handle error better
fclose(f);

// create font texture
glGenTextures(1, &_tq_texture);
glEnable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _tq_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TQ_TEXTURE_WIDTH, TQ_TEXTURE_HEIGHT-1, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, &bitmap[TQ_TEXTURE_WIDTH]); // we skip first row of bitmap because that's the indicator for where each character is. XXX: maybe use a smaller internalformat? we really only need 4-bit monochrome
glGenerateMipmap(GL_TEXTURE_2D); // XXX: maybe get rid of mipmaps idk
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);

// create the alphabet
memset(_tq_alphabet, 0, 1024*sizeof(TQ_Vertex));
int c = 32; // bitmapped font starts at char 32 (space character)
int lasti = 0;
for (int i = 0; i<=TQ_TEXTURE_WIDTH; i++) {
if (bitmap[i]||i==TQ_TEXTURE_WIDTH) {
float x = (float)(i-lasti)/TQ_TEXTURE_HEIGHT;
float tx = (i-0.5f)/TQ_TEXTURE_WIDTH;
float lasttx = (lasti+0.5f)/TQ_TEXTURE_WIDTH;
lasti = i;
_tq_alphabet[c*4 ].x = x;
_tq_alphabet[c*4 ].y = -1.f;
_tq_alphabet[c*4 ].tx= tx;
_tq_alphabet[c*4 ].ty= 1;
_tq_alphabet[c*4+1].x = x;
_tq_alphabet[c*4+1].y = 0.f;
_tq_alphabet[c*4+1].tx= tx;
_tq_alphabet[c*4+1].ty= 0;
_tq_alphabet[c*4+2].x = 0;
_tq_alphabet[c*4+2].y = 0.f;
_tq_alphabet[c*4+2].tx= lasttx;
_tq_alphabet[c*4+2].ty= 0;
_tq_alphabet[c*4+3].x = 0;
_tq_alphabet[c*4+3].y = -1.f;
_tq_alphabet[c*4+3].tx= lasttx;
_tq_alphabet[c*4+3].ty= 1;
c++;
}
}
free(bitmap);
}

void tq_mode() {
glEnable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, _tq_texture);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
}

void tq_draw(TQ_Drawable td) {
glVertexPointer (2, GL_FLOAT, sizeof(TQ_Vertex), &td.v[0].x);
glTexCoordPointer(2, GL_FLOAT, sizeof(TQ_Vertex), &td.v[0].tx);
glDrawArrays(GL_QUADS, 0, td.n);
}

TQ_Drawable tq_centered_fitted(const char *str, float width, float height) { // Nominal font size is 1. Actual font size may vary slightly to fit.
TQ_Drawable td; td.n=0; td.v=NULL; td.isComplete=0;
if (!str )return td; // null string
if (!str[0])return td; // blank string
td.v = malloc((strlen(str)+3+1) * 4 * sizeof(TQ_Vertex));
if (!td.v )return td; // malloc error
const float SPACING = 0.05f;
const char *p = str;
float x=0, y=0;
const char *ls = p; // line start
const char *le = p; // line end
float lw = 0; // line width
float widest=0;// widest line
while (*p && y > -height+0.99f) {
// determine where the next line should end...
lw = x = 0;
while (1) {
if (*p=='\0'||*p=='\n'){ le=p; lw=x; break; }
if (isspace(*p)) { le=p; lw=x; }
x += _tq_alphabet[*(unsigned char*)p * 4].x + SPACING;
if (x >= width && lw>0) { break; }
if (*p=='-' || *p==','){ le=p; lw=x; }
p++;
} lw -= SPACING;
// generate quads of that line...
if (lw <= width) { // usual case
x = -0.5f * lw;
if (widest<lw) widest=lw;
for (p=ls; p<=le; p++) {
int base = *(unsigned char*)p * 4;
if (*p != ' ') { // skipping spaces is an optimization
for (int i=0;i<4;i++) {
td.v[td.n] = _tq_alphabet[base+i];
td.v[td.n].x += x;
td.v[td.n].y += y;
td.n++;
}
} x += _tq_alphabet[base].x + SPACING;
} y -= 1.f;
}
else { // case where line is one word and too wide: shrink
x = -0.5f * width;
widest = width;
float scale = width/lw;
float spacing = SPACING*scale;
for (p=ls; p<=le; p++) {
int base = *(unsigned char*)p * 4;
if (*p != ' ') {
for (int i=0;i<4;i++) {
td.v[td.n] = _tq_alphabet[base+i];
td.v[td.n].x *= scale;
td.v[td.n].x += x;
td.v[td.n].y *= scale;
td.v[td.n].y += y;
td.n++;
}
} x += _tq_alphabet[base].x*scale + spacing;
} y -= scale;
}
if (*le == '\0') { td.isComplete = 1; break; }
ls = p = ++le;
}
// expand text if small
if (widest < width && y > -height) {
float sx = width/widest;
float sy = -height/y;
float scale = sx<sy?sx:sy;
for (int i=0; i<td.n; i++) {
td.v[i].x *= scale;
td.v[i].y *= scale;
} y *= scale;
}
// add ellipsis if text didn't all fit
if (*le) {
int base = 4 * (unsigned char)'.';
for (int h=0;h<3;h++) {
x = 0.5f*lw + h * (_tq_alphabet[base].x + 0.02f);
for (int i=0;i<4;i++) {
td.v[td.n] = _tq_alphabet[base+i];
td.v[td.n].x += x;
td.v[td.n].y += y + 1.f;
td.n++;
}
}
}
// center vertically
y *= 0.5f; for (int i=0; i<td.n; i++) td.v[i].y -= y;
// done
return td;
}

void tq_delete(TQ_Drawable *td) {
free(td->v); td->v = NULL;
td->n = 0; td->isComplete = 0;
}

void tq_done() {
glDeleteTextures(1, &_tq_texture);
}
</syntaxhighlight>

Code:text-quads.h - Revision history

Elie at 13:40, 30 November 2022

Elie at 13:37, 30 November 2022