Text: add function to get character position by index, use same character loop everywhere

2 files changed, 106 insertions, 46 deletions

diff --git a/include/mgl/graphics/text.h b/include/mgl/graphics/text.h
index a645b0b..08a6c37 100644
--- a/include/mgl/graphics/text.h
+++ b/include/mgl/graphics/text.h
@@ -41,6 +41,8 @@ void mgl_text_set_font(mgl_text *self, mgl_font *font);
 void mgl_text_set_position(mgl_text *self, mgl_vec2f position);
 void mgl_text_set_color(mgl_text *self, mgl_color color);
 mgl_vec2f mgl_text_get_bounds(const mgl_text *self);
+/* Returns the position of the character on the screen (relative to the current mgl_view) */
+mgl_vec2f mgl_text_find_character_pos(mgl_text *self, size_t index);
 void mgl_text_draw(mgl_context *context, mgl_text *text);
 
 #endif /* MGL_TEXT_H */
diff --git a/src/graphics/text.c b/src/graphics/text.c
index ea60b6a..cd9d0d9 100644
--- a/src/graphics/text.c
+++ b/src/graphics/text.c
@@ -8,18 +8,11 @@
 
 #define TAB_WIDTH 4
 
-static float max_float(float a, float b) {
-    return a >= b ? a : b;
-}
-
-static mgl_vec2f mgl_text_calculate_bounds(mgl_text *self) {
-    mgl_vec2f bounds;
-    bounds.x = 0.0f;
-    bounds.y = self->font->character_size;
-
-    /* TODO: Combine this with the loop in mgl_text_draw */
+/* Return false to stop the loop. |glyph| is not valid if codepoint is '\n' */
+typedef bool (*codepoint_loop_callback)(size_t codepoint_index, uint32_t codepoint, const mgl_font_glyph *glyph, void *userdata);
+static void mgl_text_for_each_codepoint(const mgl_text *self, codepoint_loop_callback callback, void *userdata) {
     mgl_font_glyph glyph;
-    float width = 0.0f;
+    size_t codepoint_index = 0;
     for(size_t i = 0; i < self->text_size;) {
         unsigned char *cp = (unsigned char*)&self->text[i];
         uint32_t codepoint;
@@ -31,22 +24,57 @@ static mgl_vec2f mgl_text_calculate_bounds(mgl_text *self) {
 
         if(codepoint == '\t') {
             if(mgl_font_get_glyph(self->font, ' ', &glyph) == 0) {
-                width += (glyph.advance * TAB_WIDTH);
-                bounds.x = max_float(bounds.x, width);
+                if(!callback(codepoint_index, codepoint, &glyph, userdata))
+                    return;
             }
         } else if(codepoint == '\n') {
-            width = 0.0f;
-            bounds.y += self->font->character_size;
+            if(!callback(codepoint_index, codepoint, &glyph, userdata))
+                return;
         } else {
             if(mgl_font_get_glyph(self->font, codepoint, &glyph) == 0) {
-                width += glyph.advance;
-                bounds.x = max_float(bounds.x, width);
+                if(!callback(codepoint_index, codepoint, &glyph, userdata))
+                    return;
             }
         }
         i += clen;
+        ++codepoint_index;
+    }
+}
+
+static float max_float(float a, float b) {
+    return a >= b ? a : b;
+}
+
+typedef struct {
+    mgl_vec2f bounds;
+    float line_width;
+    const mgl_font *font;
+} CalculateBoundsUserdata;
+
+static bool calculate_bounds_callback(size_t codepoint_index, uint32_t codepoint, const mgl_font_glyph *glyph, void *userdata) {
+    (void)codepoint_index;
+    CalculateBoundsUserdata *calculate_bounds_userdata = userdata;
+    if(codepoint == '\t') {
+        calculate_bounds_userdata->line_width += (glyph->advance * TAB_WIDTH);
+        calculate_bounds_userdata->bounds.x = max_float(calculate_bounds_userdata->bounds.x, calculate_bounds_userdata->line_width);
+    } else if(codepoint == '\n') {
+        calculate_bounds_userdata->line_width = 0.0f;
+        calculate_bounds_userdata->bounds.y += calculate_bounds_userdata->font->character_size;
+    } else {
+        calculate_bounds_userdata->line_width += glyph->advance;
+        calculate_bounds_userdata->bounds.x = max_float(calculate_bounds_userdata->bounds.x, calculate_bounds_userdata->line_width);
     }
+    return true;
+}
 
-    return bounds;
+static mgl_vec2f mgl_text_calculate_bounds(mgl_text *self) {
+    CalculateBoundsUserdata calculate_bounds_userdata;
+    calculate_bounds_userdata.bounds.x = 0.0f;
+    calculate_bounds_userdata.bounds.y = self->font->character_size;
+    calculate_bounds_userdata.line_width = 0.0f;
+    calculate_bounds_userdata.font = self->font;
+    mgl_text_for_each_codepoint(self, calculate_bounds_callback, &calculate_bounds_userdata);
+    return calculate_bounds_userdata.bounds;
 }
 
 void mgl_text_init(mgl_text *self, mgl_font *font, const char *str, size_t str_size) {
@@ -97,7 +125,38 @@ mgl_vec2f mgl_text_get_bounds(const mgl_text *self) {
     return self->bounds;
 }
 
-static void mgl_text_draw_glyph(mgl_context *context, mgl_font_glyph *glyph, mgl_vec2i position) {
+typedef struct {
+    mgl_vec2i position;
+    const mgl_text *text;
+    size_t index;
+} FindCharacterPosUserdata;
+
+static bool find_character_pos_callback(size_t codepoint_index, uint32_t codepoint, const mgl_font_glyph *glyph, void *userdata) {
+    FindCharacterPosUserdata *find_character_pos_userdata = userdata;
+    if(codepoint_index >= find_character_pos_userdata->index)
+        return false;
+
+    if(codepoint == '\t') {
+        find_character_pos_userdata->position.x += (glyph->advance * TAB_WIDTH);
+    } else if(codepoint == '\n') {
+        find_character_pos_userdata->position.x = find_character_pos_userdata->text->position.x;
+        find_character_pos_userdata->position.y += find_character_pos_userdata->text->font->character_size;
+    } else {
+        find_character_pos_userdata->position.x += glyph->advance;
+    }
+    return true;
+}
+
+mgl_vec2f mgl_text_find_character_pos(mgl_text *self, size_t index) {
+    FindCharacterPosUserdata find_character_pos_userdata;
+    find_character_pos_userdata.position = (mgl_vec2i){ self->position.x, self->position.y };
+    find_character_pos_userdata.text = self;
+    find_character_pos_userdata.index = index;
+    mgl_text_for_each_codepoint(self, find_character_pos_callback, &find_character_pos_userdata);
+    return (mgl_vec2f){ find_character_pos_userdata.position.x, find_character_pos_userdata.position.y };
+}
+
+static void mgl_text_draw_glyph(mgl_context *context, const mgl_font_glyph *glyph, mgl_vec2i position) {
     context->gl.glTexCoord2f(glyph->texture_position.x, glyph->texture_position.y);
     context->gl.glVertex3f(position.x + glyph->position.x, position.y + glyph->position.y, 0.0f);
 
@@ -111,43 +170,42 @@ static void mgl_text_draw_glyph(mgl_context *context, mgl_font_glyph *glyph, mgl
     context->gl.glVertex3f(position.x + glyph->position.x, position.y + glyph->position.y + glyph->size.y, 0.0f);
 }
 
+typedef struct {
+    mgl_vec2i position;
+    const mgl_text *text;
+    mgl_context *context;
+} TextDrawUserdata;
+
+static bool text_draw_callback(size_t codepoint_index, uint32_t codepoint, const mgl_font_glyph *glyph, void *userdata) {
+    (void)codepoint_index;
+    TextDrawUserdata *text_draw_userdata = userdata;
+    if(codepoint == '\t') {
+        text_draw_userdata->position.x += (glyph->advance * TAB_WIDTH);
+    } else if(codepoint == '\n') {
+        text_draw_userdata->position.x = text_draw_userdata->text->position.x;
+        text_draw_userdata->position.y += text_draw_userdata->text->font->character_size;
+    } else {
+        mgl_text_draw_glyph(text_draw_userdata->context, glyph, text_draw_userdata->position);
+        text_draw_userdata->position.x += glyph->advance;
+    }
+    return true;
+}
+
 /* TODO: Use opengl buffer object instead */
 /* TODO: Cache texture bind to not bind texture if its already bound and do not bind texture 0 */
 void mgl_text_draw(mgl_context *context, mgl_text *text) {
     if(!text->text || text->text_size == 0 || !text->font)
         return;
 
-    mgl_font_glyph glyph;
-    mgl_vec2i position = (mgl_vec2i){ text->position.x, text->position.y };
-    position.y += text->font->character_size;
+    TextDrawUserdata text_draw_userdata;
+    text_draw_userdata.position = (mgl_vec2i){ text->position.x, text->position.y + text->font->character_size };
+    text_draw_userdata.text = text;
+    text_draw_userdata.context = context;
 
     context->gl.glColor4ub(text->color.r, text->color.g, text->color.b, text->color.a);
     mgl_texture_use(&text->font->texture);
     context->gl.glBegin(GL_QUADS);
-    for(size_t i = 0; i < text->text_size;) {
-        unsigned char *cp = (unsigned char*)&text->text[i];
-        uint32_t codepoint;
-        size_t clen;
-        if(!mgl_utf8_decode(cp, text->text_size - i, &codepoint, &clen)) {
-            codepoint = *cp;
-            clen = 1;
-        }
-
-        if(codepoint == '\t') {
-            if(mgl_font_get_glyph(text->font, ' ', &glyph) == 0) {
-                position.x += (glyph.advance * TAB_WIDTH);
-            }
-        } else if(codepoint == '\n') {
-            position.x = text->position.x;
-            position.y += text->font->character_size;
-        } else {
-            if(mgl_font_get_glyph(text->font, codepoint, &glyph) == 0) {
-                mgl_text_draw_glyph(context, &glyph, position);
-                position.x += glyph.advance;
-            }
-        }
-        i += clen;
-    }
+    mgl_text_for_each_codepoint(text, text_draw_callback, &text_draw_userdata);
     context->gl.glEnd();
     mgl_texture_use(NULL);
 }