API for changing the background image of OS windows

Uses reference counting

kitty/child-monitor.c

@@ -689,7 +689,7 @@ render(monotonic_t now, bool input_read) {
         if (!w->fonts_data) { log_error("No fonts data found for window id: %llu", w->id); continue; }
         if (prepare_to_render_os_window(w, now, &active_window_id, &active_window_bg, &num_visible_windows, &all_windows_have_same_bg)) needs_render = true;
         if (w->last_active_window_id != active_window_id || w->last_active_tab != w->active_tab || w->focused_at_last_render != w->is_focused) needs_render = true;
-        if (w->render_calls < 3 && w->bgimage.texture_id) needs_render = true;
+        if (w->render_calls < 3 && w->bgimage && w->bgimage->texture_id) needs_render = true;
         if (needs_render) render_os_window(w, now, active_window_id, active_window_bg, num_visible_windows, all_windows_have_same_bg);
     }
     last_render_at = now;

kitty/graphics.h

@@ -59,7 +59,7 @@ typedef struct {
     uint32_t texture_id;
     unsigned int height, width;
     uint8_t* bitmap;
-    bool load_failed, needs_free;
+    uint32_t refcnt;
 } BackgroundImage;
 
 typedef struct {

kitty/shaders.c

@@ -355,9 +355,9 @@ draw_bg(OSWindow *w) {
         bgimage_constants_set = true;
     }
     glUniform4f(bgimage_program_layout.sizes_location,
-        (GLfloat)w->window_width, (GLfloat)w->window_height, (GLfloat)w->bgimage.width, (GLfloat)w->bgimage.height);
+        (GLfloat)w->window_width, (GLfloat)w->window_height, (GLfloat)w->bgimage->width, (GLfloat)w->bgimage->height);
     glActiveTexture(GL_TEXTURE0 + BGIMAGE_UNIT);
-    glBindTexture(GL_TEXTURE_2D, w->bgimage.texture_id);
+    glBindTexture(GL_TEXTURE_2D, w->bgimage->texture_id);
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
     unbind_vertex_array();
     unbind_program();
@@ -428,6 +428,11 @@ draw_cells_simple(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen) {
     }
 }
 
+static inline bool
+has_bgimage(OSWindow *w) {
+    return w->bgimage && w->bgimage->texture_id > 0;
+}
+
 static void
 draw_cells_interleaved(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen, OSWindow *w) {
     glEnable(GL_BLEND);
@@ -435,12 +440,12 @@ draw_cells_interleaved(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen, OSWind
 
     bind_program(CELL_BG_PROGRAM);
     // draw background for all cells
-    if (!w->bgimage.texture_id) {
+    if (!has_bgimage(w)) {
         glUniform1ui(cell_program_layouts[CELL_BG_PROGRAM].draw_bg_bitfield_location, 3);
         glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, screen->lines * screen->columns);
     }
 
-    if (screen->grman->num_of_below_refs || w->bgimage.texture_id) {
+    if (screen->grman->num_of_below_refs || has_bgimage(w)) {
         if (screen->grman->num_of_below_refs) draw_graphics(
                 GRAPHICS_PROGRAM, vao_idx, gvao_idx, screen->grman->render_data, 0, screen->grman->num_of_below_refs);
         bind_program(CELL_BG_PROGRAM);
@@ -479,7 +484,7 @@ draw_cells_interleaved_premult(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen
     glFramebufferTexture(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, os_window->offscreen_texture_id, 0);
     /* if (glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) fatal("Offscreen framebuffer not complete"); */
     bind_program(CELL_BG_PROGRAM);
-    if (!os_window->bgimage.texture_id) {
+    if (!has_bgimage(os_window)) {
         // draw background for all cells
         glUniform1ui(cell_program_layouts[CELL_BG_PROGRAM].draw_bg_bitfield_location, 3);
         glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, screen->lines * screen->columns);
@@ -487,7 +492,7 @@ draw_cells_interleaved_premult(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen
     glEnable(GL_BLEND);
     BLEND_PREMULT;
 
-    if (screen->grman->num_of_below_refs || os_window->bgimage.texture_id) {
+    if (screen->grman->num_of_below_refs || has_bgimage(os_window)) {
         if (screen->grman->num_of_below_refs) draw_graphics(
             GRAPHICS_PREMULT_PROGRAM, vao_idx, gvao_idx, screen->grman->render_data, 0, screen->grman->num_of_below_refs);
         bind_program(CELL_BG_PROGRAM);
@@ -513,7 +518,7 @@ draw_cells_interleaved_premult(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen
     if (screen->grman->num_of_positive_refs) draw_graphics(GRAPHICS_PREMULT_PROGRAM, vao_idx, gvao_idx, screen->grman->render_data, screen->grman->num_of_negative_refs + screen->grman->num_of_below_refs, screen->grman->num_of_positive_refs);
 
     glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-    if (!os_window->bgimage.texture_id) glDisable(GL_BLEND);
+    if (!has_bgimage(os_window)) glDisable(GL_BLEND);
     glEnable(GL_SCISSOR_TEST);
 
     // Now render the framebuffer to the screen
@@ -602,10 +607,10 @@ draw_cells(ssize_t vao_idx, ssize_t gvao_idx, GLfloat xstart, GLfloat ystart, GL
     );
 #undef SCALE
     if (os_window->is_semi_transparent) {
-        if (screen->grman->count || os_window->bgimage.texture_id) draw_cells_interleaved_premult(vao_idx, gvao_idx, screen, os_window);
+        if (screen->grman->count || has_bgimage(os_window)) draw_cells_interleaved_premult(vao_idx, gvao_idx, screen, os_window);
         else draw_cells_simple(vao_idx, gvao_idx, screen);
     } else {
-        if (screen->grman->num_of_negative_refs || screen->grman->num_of_below_refs || os_window->bgimage.texture_id) draw_cells_interleaved(vao_idx, gvao_idx, screen, os_window);
+        if (screen->grman->num_of_negative_refs || screen->grman->num_of_below_refs || has_bgimage(os_window)) draw_cells_interleaved(vao_idx, gvao_idx, screen, os_window);
         else draw_cells_simple(vao_idx, gvao_idx, screen);
     }
 }
@@ -649,7 +654,7 @@ create_border_vao(void) {
 void
 draw_borders(ssize_t vao_idx, unsigned int num_border_rects, BorderRect *rect_buf, bool rect_data_is_dirty, uint32_t viewport_width, uint32_t viewport_height, color_type active_window_bg, unsigned int num_visible_windows, bool all_windows_have_same_bg, OSWindow *w) {
 
-    if (w->bgimage.texture_id) {
+    if (has_bgimage(w)) {
         glEnable(GL_BLEND);
         BLEND_ONTO_OPAQUE;
         draw_bg(w);
@@ -677,7 +682,7 @@ draw_borders(ssize_t vao_idx, unsigned int num_border_rects, BorderRect *rect_bu
         unbind_vertex_array();
         unbind_program();
     }
-    if (w->bgimage.texture_id) glDisable(GL_BLEND);
+    if (has_bgimage(w)) glDisable(GL_BLEND);
 }
 
 // }}}

kitty/state.c

@@ -71,6 +71,37 @@ os_window_for_kitty_window(id_type kitty_window_id) {
     return NULL;
 }
 
+static void
+send_bgimage_to_gpu(BackgroundImageLayout layout, BackgroundImage *bgimage) {
+    RepeatStrategy r;
+    switch (layout) {
+        case SCALED:
+            r = REPEAT_CLAMP; break;
+        case MIRRORED:
+            r = REPEAT_MIRROR; break;
+        case TILING:
+        default:
+            r = REPEAT_DEFAULT; break;
+    }
+    bgimage->texture_id = 0;
+    send_image_to_gpu(&bgimage->texture_id, bgimage->bitmap, bgimage->width,
+            bgimage->height, false, true, OPT(background_image_linear), r);
+    free(bgimage->bitmap); bgimage->bitmap = NULL;
+}
+
+static void
+free_bgimage(BackgroundImage *bgimage, bool release_texture) {
+    if (bgimage && bgimage->refcnt) {
+        bgimage->refcnt--;
+        if (bgimage->refcnt == 0) {
+            free(bgimage->bitmap); bgimage->bitmap = NULL;
+            if (release_texture) free_texture(&bgimage->texture_id);
+        }
+    }
+}
+
+static BackgroundImage global_bg_image = {0};
+
 OSWindow*
 add_os_window() {
     WITH_OS_WINDOW_REFS
@@ -84,29 +115,17 @@ add_os_window() {
 
     bool wants_bg = OPT(background_image) && OPT(background_image)[0] != 0;
     if (wants_bg) {
-        if (!global_state.bgimage.texture_id && !global_state.bgimage.load_failed) {
+        if (!global_state.bgimage) {
+            global_state.bgimage = &global_bg_image;
+            global_state.bgimage->refcnt++;
             size_t size;
-            if (png_path_to_bitmap(OPT(background_image), &global_state.bgimage.bitmap, &global_state.bgimage.width, &global_state.bgimage.height, &size)) {
+            if (png_path_to_bitmap(OPT(background_image), &global_state.bgimage->bitmap, &global_state.bgimage->width, &global_state.bgimage->height, &size)) {
-                RepeatStrategy r;
+                send_bgimage_to_gpu(OPT(background_image_layout), global_state.bgimage);
-                switch (OPT(background_image_layout)) {
+            }
-                    case SCALED:
-                        r = REPEAT_CLAMP; break;
-                    case MIRRORED:
-                        r = REPEAT_MIRROR; break;
-                    case TILING:
-                    default:
-                        r = REPEAT_DEFAULT; break;
-                }
-                global_state.bgimage.texture_id = 0;
-                send_image_to_gpu(&global_state.bgimage.texture_id, global_state.bgimage.bitmap, global_state.bgimage.width,
-                        global_state.bgimage.height, false, true, OPT(background_image_linear), r);
-                global_state.bgimage.needs_free = true;
-                free(global_state.bgimage.bitmap); global_state.bgimage.bitmap = NULL;
-            } else global_state.bgimage.load_failed = true;
         }
-        if (global_state.bgimage.texture_id) {
+        if (global_state.bgimage->texture_id) {
-            memcpy(&ans->bgimage, &global_state.bgimage, sizeof(global_state.bgimage));
+            ans->bgimage = global_state.bgimage;
-            ans->bgimage.needs_free = false;
+            ans->bgimage->refcnt++;
         }
     }
 
@@ -288,9 +307,8 @@ destroy_os_window_item(OSWindow *w) {
     remove_vao(w->tab_bar_render_data.vao_idx);
     remove_vao(w->gvao_idx);
     free(w->tabs); w->tabs = NULL;
-    if (w->bgimage.needs_free) {
+    free_bgimage(w->bgimage, true);
-        free(w->bgimage.bitmap); free_texture(&w->bgimage.texture_id);
+    w->bgimage = NULL;
-    }
 }
 
 bool
@@ -884,6 +902,44 @@ PYWRAP1(patch_global_colors) {
     Py_RETURN_NONE;
 }
 
+static PyObject*
+pyset_background_image(PyObject *self UNUSED, PyObject *args) {
+    const char *path;
+    PyObject *layout_name = NULL;
+    PyObject *os_window_ids;
+    int configured = 0;
+    PA("sO&|pU", &path, &PyTuple_Type, &os_window_ids, &configured, &layout_name);
+    size_t size;
+    BackgroundImageLayout layout = layout_name ? bglayout(layout_name) : OPT(background_image_layout);
+    BackgroundImage *bgimage = calloc(1, sizeof(BackgroundImage));
+    if (!bgimage) return PyErr_NoMemory();
+    if (!png_path_to_bitmap(path, &bgimage->bitmap, &bgimage->width, &bgimage->height, &size)) {
+        PyErr_Format(PyExc_ValueError, "Failed to load image from: %s", path);
+        free(bgimage);
+        return NULL;
+    }
+    send_bgimage_to_gpu(layout, bgimage);
+    bgimage->refcnt++;
+    if (configured) {
+        free_bgimage(global_state.bgimage, true);
+        global_state.bgimage = bgimage;
+        bgimage->refcnt++;
+        OPT(background_image_layout) = layout;
+    }
+    for (Py_ssize_t i = 0; i < PyTuple_GET_SIZE(os_window_ids); i++) {
+        id_type os_window_id = PyLong_AsUnsignedLongLong(PyTuple_GET_ITEM(os_window_ids, i));
+        WITH_OS_WINDOW(os_window_id)
+            make_os_window_context_current(os_window);
+            free_bgimage(os_window->bgimage, true);
+            os_window->bgimage = bgimage;
+            os_window->render_calls = 0;
+            bgimage->refcnt++;
+        END_WITH_OS_WINDOW
+    }
+    free_bgimage(bgimage, true);
+    Py_RETURN_NONE;
+}
+
 PYWRAP0(destroy_global_data) {
     Py_CLEAR(global_state.boss);
     free(global_state.os_windows); global_state.os_windows = NULL;
@@ -940,6 +996,7 @@ static PyMethodDef module_methods[] = {
     MW(background_opacity_of, METH_O),
     MW(update_window_visibility, METH_VARARGS),
     MW(global_font_size, METH_VARARGS),
+    MW(set_background_image, METH_VARARGS),
     MW(os_window_font_size, METH_VARARGS),
     MW(set_boss, METH_O),
     MW(patch_global_colors, METH_VARARGS),
@@ -956,13 +1013,12 @@ finalize(void) {
     if (detached_windows.windows) free(detached_windows.windows);
     detached_windows.capacity = 0;
     if (OPT(background_image)) free(OPT(background_image));
-    if (global_state.bgimage.needs_free) {
+    // we leak the texture here since it is not guaranteed
-        free(global_state.bgimage.bitmap);
+    // that freeing the texture will work during shutdown and
-        // we leak the texture here since it is not guaranteed
+    // the GPU driver should take care of it when the OpenGL context is
-        // that freeing the texture will work during shutdown and
+    // destroyed.
-        // the GPU driver should take care of it when the OpenGL context is
+    free_bgimage(global_state.bgimage, false);
-        // destroyed.
+    global_state.bgimage = NULL;
-    }
 }
 
 bool

kitty/state.h

@@ -142,7 +142,7 @@ typedef struct {
     int viewport_width, viewport_height, window_width, window_height;
     double viewport_x_ratio, viewport_y_ratio;
     Tab *tabs;
-    BackgroundImage bgimage;
+    BackgroundImage *bgimage;
     unsigned int active_tab, num_tabs, capacity, last_active_tab, last_num_tabs, last_active_window_id;
     bool focused_at_last_render, needs_render;
     ScreenRenderData tab_bar_render_data;
@@ -176,7 +176,7 @@ typedef struct {
 
     id_type os_window_id_counter, tab_id_counter, window_id_counter;
     PyObject *boss;
-    BackgroundImage bgimage;
+    BackgroundImage *bgimage;
     OSWindow *os_windows;
     size_t num_os_windows, capacity;
     OSWindow *callback_os_window;