macOS: Fix a crash when rendering ligatures larger than 128 characters

Fixes #3724

docs/changelog.rst

@@ -10,6 +10,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - macOS: Fix a regression in the previous release that broke rendering of
   strikeout (:iss:`3717`)
 
+- macOS: Fix a crash when rendering ligatures larger than 128 characters
+  (:iss:`3724`)
+
 - Fix a regression in the previous release that could cause a crash when
   changing layouts and mousing (:iss:`3713`)
 

kitty/core_text.m

@@ -415,16 +415,20 @@ specialize_font_descriptor(PyObject *base_descriptor, FONTS_DATA_HANDLE fg UNUSE
     return base_descriptor;
 }
 
-static uint8_t *render_buf = NULL;
+struct RenderBuffers {
-static size_t render_buf_sz = 0;
+    uint8_t *render_buf;
-static CGGlyph glyphs[128];
+    size_t render_buf_sz, sz;
-static CGRect boxes[128];
+    CGGlyph *glyphs;
-static CGPoint positions[128];
+    CGRect *boxes;
-static CGSize advances[128];
+    CGPoint *positions;
+    CGSize *advances;
+};
+static struct RenderBuffers buffers = {0};
 
 static void
 finalize(void) {
-    free(render_buf);
+    free(buffers.render_buf); free(buffers.glyphs); free(buffers.boxes); free(buffers.positions); free(buffers.advances);
+    memset(&buffers, 0, sizeof(struct RenderBuffers));
     if (all_fonts_collection_data) CFRelease(all_fonts_collection_data);
 }
 
@@ -442,7 +446,7 @@ render_color_glyph(CTFontRef font, uint8_t *buf, int glyph_id, unsigned int widt
     CGContextSetTextDrawingMode(ctx, kCGTextFill);
     CGGlyph glyph = glyph_id;
     CGContextSetTextMatrix(ctx, transform);
-    CGContextSetTextPosition(ctx, -boxes[0].origin.x, MAX(2, height - baseline));
+    CGContextSetTextPosition(ctx, -buffers.boxes[0].origin.x, MAX(2, height - baseline));
     CGPoint p = CGPointMake(0, 0);
     CTFontDrawGlyphs(font, &glyph, &p, 1, ctx);
     CGContextRelease(ctx);
@@ -455,21 +459,30 @@ render_color_glyph(CTFontRef font, uint8_t *buf, int glyph_id, unsigned int widt
     }
 }
 
-static inline void
+static void
-ensure_render_space(size_t width, size_t height) {
+ensure_render_space(size_t width, size_t height, size_t num_glyphs) {
-    if (render_buf_sz >= width * height) return;
+    if (buffers.render_buf_sz < width * height) {
-    free(render_buf);
+        free(buffers.render_buf); buffers.render_buf = NULL;
-    render_buf_sz = width * height;
+        buffers.render_buf_sz = width * height;
-    render_buf = malloc(render_buf_sz);
+        buffers.render_buf = malloc(buffers.render_buf_sz);
-    if (render_buf == NULL) fatal("Out of memory");
+        if (buffers.render_buf == NULL) fatal("Out of memory");
+    }
+    if (buffers.sz < num_glyphs) {
+        buffers.sz = MAX(128, num_glyphs * 2);
+        buffers.advances = calloc(sizeof(buffers.advances[0]), buffers.sz);
+        buffers.boxes = calloc(sizeof(buffers.boxes[0]), buffers.sz);
+        buffers.glyphs = calloc(sizeof(buffers.glyphs[0]), buffers.sz);
+        buffers.positions = calloc(sizeof(buffers.positions[0]), buffers.sz);
+        if (!buffers.advances || !buffers.boxes || !buffers.glyphs || !buffers.positions) fatal("Out of memory");
+    }
 }
 
 static inline void
 render_glyphs(CTFontRef font, unsigned int width, unsigned int height, unsigned int baseline, unsigned int num_glyphs) {
-    memset(render_buf, 0, width * height);
+    memset(buffers.render_buf, 0, width * height);
     CGColorSpaceRef gray_color_space = CGColorSpaceCreateDeviceGray();
     if (gray_color_space == NULL) fatal("Out of memory");
-    CGContextRef render_ctx = CGBitmapContextCreate(render_buf, width, height, 8, width, gray_color_space, (kCGBitmapAlphaInfoMask & kCGImageAlphaNone));
+    CGContextRef render_ctx = CGBitmapContextCreate(buffers.render_buf, width, height, 8, width, gray_color_space, (kCGBitmapAlphaInfoMask & kCGImageAlphaNone));
     if (render_ctx == NULL) fatal("Out of memory");
     CGContextSetShouldAntialias(render_ctx, true);
     CGContextSetShouldSmoothFonts(render_ctx, true);
@@ -479,7 +492,7 @@ render_glyphs(CTFontRef font, unsigned int width, unsigned int height, unsigned
     CGContextSetTextDrawingMode(render_ctx, kCGTextFillStroke);
     CGContextSetTextMatrix(render_ctx, CGAffineTransformIdentity);
     CGContextSetTextPosition(render_ctx, 0, height - baseline);
-    CTFontDrawGlyphs(font, glyphs, positions, num_glyphs, render_ctx);
+    CTFontDrawGlyphs(font, buffers.glyphs, buffers.positions, num_glyphs, render_ctx);
     CGContextRelease(render_ctx);
     CGColorSpaceRelease(gray_color_space);
 }
@@ -492,19 +505,20 @@ render_simple_text_impl(PyObject *s, const char *text, unsigned int baseline) {
     unichar chars[num_chars];
     CGSize local_advances[num_chars];
     for (size_t i = 0; i < num_chars; i++) chars[i] = text[i];
-    CTFontGetGlyphsForCharacters(font, chars, glyphs, num_chars);
+    ensure_render_space(0, 0, num_chars);
-    CTFontGetAdvancesForGlyphs(font, kCTFontOrientationDefault, glyphs, local_advances, num_chars);
+    CTFontGetGlyphsForCharacters(font, chars, buffers.glyphs, num_chars);
-    CGRect bounding_box = CTFontGetBoundingRectsForGlyphs(font, kCTFontOrientationDefault, glyphs, boxes, num_chars);
+    CTFontGetAdvancesForGlyphs(font, kCTFontOrientationDefault, buffers.glyphs, local_advances, num_chars);
+    CGRect bounding_box = CTFontGetBoundingRectsForGlyphs(font, kCTFontOrientationDefault, buffers.glyphs, buffers.boxes, num_chars);
     CGFloat x = 0, y = 0;
     for (size_t i = 0; i < num_chars; i++) {
-        positions[i] = CGPointMake(x, y);
+        buffers.positions[i] = CGPointMake(x, y);
         x += local_advances[i].width; y += local_advances[i].height;
     }
     StringCanvas ans = { .width = (size_t)ceil(x), .height = (size_t)(2 * bounding_box.size.height) };
-    ensure_render_space(ans.width, ans.height);
+    ensure_render_space(ans.width, ans.height, num_chars);
     render_glyphs(font, ans.width, ans.height, baseline, num_chars);
     ans.canvas = malloc(ans.width * ans.height);
-    if (ans.canvas) memcpy(ans.canvas, render_buf, ans.width * ans.height);
+    if (ans.canvas) memcpy(ans.canvas, buffers.render_buf, ans.width * ans.height);
     return ans;
 }
 
@@ -512,12 +526,13 @@ render_simple_text_impl(PyObject *s, const char *text, unsigned int baseline) {
 static inline bool
 do_render(CTFontRef ct_font, bool bold, bool italic, hb_glyph_info_t *info, hb_glyph_position_t *hb_positions, unsigned int num_glyphs, pixel *canvas, unsigned int cell_width, unsigned int cell_height, unsigned int num_cells, unsigned int baseline, bool *was_colored, bool allow_resize, FONTS_DATA_HANDLE fg, bool center_glyph) {
     unsigned int canvas_width = cell_width * num_cells;
-    CGRect br = CTFontGetBoundingRectsForGlyphs(ct_font, kCTFontOrientationHorizontal, glyphs, boxes, num_glyphs);
+    ensure_render_space(canvas_width, cell_height, num_glyphs);
+    CGRect br = CTFontGetBoundingRectsForGlyphs(ct_font, kCTFontOrientationHorizontal, buffers.glyphs, buffers.boxes, num_glyphs);
     const bool debug_rendering = false;
     if (allow_resize) {
         // Resize glyphs that would bleed into neighboring cells, by scaling the font size
         float right = 0;
-        for (unsigned i=0; i < num_glyphs; i++) right = MAX(right, boxes[i].origin.x + boxes[i].size.width);
+        for (unsigned i=0; i < num_glyphs; i++) right = MAX(right, buffers.boxes[i].origin.x + buffers.boxes[i].size.width);
         if (!bold && !italic && right > canvas_width + 1) {
             if (debug_rendering) printf("resizing glyphs, right: %f canvas_width: %u\n", right, canvas_width);
             CGFloat sz = CTFontGetSize(ct_font);
@@ -529,19 +544,18 @@ do_render(CTFontRef ct_font, bool bold, bool italic, hb_glyph_info_t *info, hb_g
         }
     }
     CGFloat x = 0, y = 0;
-    CTFontGetAdvancesForGlyphs(ct_font, kCTFontOrientationDefault, glyphs, advances, num_glyphs);
+    CTFontGetAdvancesForGlyphs(ct_font, kCTFontOrientationDefault, buffers.glyphs, buffers.advances, num_glyphs);
     for (unsigned i=0; i < num_glyphs; i++) {
-        positions[i].x = x; positions[i].y = y;
+        buffers.positions[i].x = x; buffers.positions[i].y = y;
-        if (debug_rendering) printf("x=%f origin=%f width=%f advance=%f\n", x, boxes[i].origin.x, boxes[i].size.width, advances[i].width);
+        if (debug_rendering) printf("x=%f origin=%f width=%f advance=%f\n", x, buffers.boxes[i].origin.x, buffers.boxes[i].size.width, buffers.advances[i].width);
-        x += advances[i].width; y += advances[i].height;
+        x += buffers.advances[i].width; y += buffers.advances[i].height;
     }
     if (*was_colored) {
         render_color_glyph(ct_font, (uint8_t*)canvas, info[0].codepoint, cell_width * num_cells, cell_height, baseline);
     } else {
-        ensure_render_space(canvas_width, cell_height);
         render_glyphs(ct_font, canvas_width, cell_height, baseline, num_glyphs);
         Region src = {.bottom=cell_height, .right=canvas_width}, dest = {.bottom=cell_height, .right=canvas_width};
-        render_alpha_mask(render_buf, canvas, &src, &dest, canvas_width, canvas_width);
+        render_alpha_mask(buffers.render_buf, canvas, &src, &dest, canvas_width, canvas_width);
     }
     if (num_cells && (center_glyph || (num_cells == 2 && *was_colored))) {
         if (debug_rendering) printf("centering glyphs: center_glyph: %d\n", center_glyph);
@@ -557,7 +571,8 @@ do_render(CTFontRef ct_font, bool bold, bool italic, hb_glyph_info_t *info, hb_g
 bool
 render_glyphs_in_cells(PyObject *s, bool bold, bool italic, hb_glyph_info_t *info, hb_glyph_position_t *hb_positions, unsigned int num_glyphs, pixel *canvas, unsigned int cell_width, unsigned int cell_height, unsigned int num_cells, unsigned int baseline, bool *was_colored, FONTS_DATA_HANDLE fg, bool center_glyph) {
     CTFace *self = (CTFace*)s;
-    for (unsigned i=0; i < num_glyphs; i++) glyphs[i] = info[i].codepoint;
+    ensure_render_space(128, 128, num_glyphs);
+    for (unsigned i=0; i < num_glyphs; i++) buffers.glyphs[i] = info[i].codepoint;
     return do_render(self->ct_font, bold, italic, info, hb_positions, num_glyphs, canvas, cell_width, cell_height, num_cells, baseline, was_colored, true, fg, center_glyph);
 }
 

kitty/fonts.c

@@ -560,10 +560,10 @@ END_ALLOW_CASE_RANGE
 static PyObject* box_drawing_function = NULL, *prerender_function = NULL, *descriptor_for_idx = NULL;
 
 void
-render_alpha_mask(uint8_t *alpha_mask, pixel* dest, Region *src_rect, Region *dest_rect, size_t src_stride, size_t dest_stride) {
+render_alpha_mask(const uint8_t *alpha_mask, pixel* dest, Region *src_rect, Region *dest_rect, size_t src_stride, size_t dest_stride) {
     for (size_t sr = src_rect->top, dr = dest_rect->top; sr < src_rect->bottom && dr < dest_rect->bottom; sr++, dr++) {
         pixel *d = dest + dest_stride * dr;
-        uint8_t *s = alpha_mask + src_stride * sr;
+        const uint8_t *s = alpha_mask + src_stride * sr;
         for(size_t sc = src_rect->left, dc = dest_rect->left; sc < src_rect->right && dc < dest_rect->right; sc++, dc++) {
             uint8_t src_alpha = d[dc] & 0xff;
             uint8_t alpha = s[sc];

kitty/fonts.h

@@ -33,7 +33,7 @@ PyObject* face_from_descriptor(PyObject*, FONTS_DATA_HANDLE);
 const char* postscript_name_for_face(const PyObject*);
 
 void sprite_tracker_current_layout(FONTS_DATA_HANDLE data, unsigned int *x, unsigned int *y, unsigned int *z);
-void render_alpha_mask(uint8_t *alpha_mask, pixel* dest, Region *src_rect, Region *dest_rect, size_t src_stride, size_t dest_stride);
+void render_alpha_mask(const uint8_t *alpha_mask, pixel* dest, Region *src_rect, Region *dest_rect, size_t src_stride, size_t dest_stride);
 void render_line(FONTS_DATA_HANDLE, Line *line, index_type lnum, Cursor *cursor, DisableLigature);
 void sprite_tracker_set_limits(size_t max_texture_size, size_t max_array_len);
 typedef void (*free_extra_data_func)(void*);