From 65a7b19f4029bd6466c03f3556a5ab2fcb351d27 Mon Sep 17 00:00:00 2001
From: Fredrick Brennan <copypaste@kittens.ph>
Date: Fri, 24 Jan 2020 16:06:57 +0800
Subject: [PATCH] Make each OS window have its own framebuffer

This commit fixes graphics rendering when more than one OS window is
open, all OS windows are semi-transparent, and multiple windows contain
graphics.

This commit closes #2310.
---
 docs/changelog.rst | 2 ++
 kitty/gl.c         | 5 +++++
 kitty/gl.h         | 1 +
 kitty/shaders.c    | 5 ++---
 kitty/state.c      | 1 +
 kitty/state.h      | 2 ++
 6 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 74482920d..b1291567b 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -45,6 +45,8 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Fix URL detection not working for urls of the form scheme:///url
   (:iss:`2292`)
 
+- When windows are semi-transparent and all contain graphics, correctly render
+  them. (:iss:`2310`)
 
 0.15.1 [2019-12-21]
 --------------------
diff --git a/kitty/gl.c b/kitty/gl.c
index cd623c8eb..cab14738a 100644
--- a/kitty/gl.c
+++ b/kitty/gl.c
@@ -81,6 +81,11 @@ free_texture(GLuint *tex_id) {
     *tex_id = 0;
 }
 
+void
+free_framebuffer(GLuint *fb_id) {
+    glDeleteFramebuffers(1, fb_id);
+    *fb_id = 0;
+}
 
 // }}}
 
diff --git a/kitty/gl.h b/kitty/gl.h
index 2a6981cd0..520a5ae25 100644
--- a/kitty/gl.h
+++ b/kitty/gl.h
@@ -35,6 +35,7 @@ typedef struct {
 void gl_init(void);
 void update_surface_size(int w, int h, GLuint offscreen_texture_id);
 void free_texture(GLuint *tex_id);
+void free_framebuffer(GLuint *fb_id);
 void remove_vao(ssize_t vao_idx);
 void init_uniforms(int program);
 GLuint program_id(int program);
diff --git a/kitty/shaders.c b/kitty/shaders.c
index fff135352..83a0c8c42 100644
--- a/kitty/shaders.c
+++ b/kitty/shaders.c
@@ -154,7 +154,6 @@ typedef struct {
 } CellProgramLayout;
 
 static CellProgramLayout cell_program_layouts[NUM_PROGRAMS];
-static GLuint offscreen_framebuffer = 0;
 static ssize_t blit_vertex_array;
 
 static void
@@ -173,7 +172,6 @@ init_cell_program(void) {
         C(p, colors, 0); C(p, sprite_coords, 1); C(p, is_selected, 2);
     }
 #undef C
-    glGenFramebuffers(1, &offscreen_framebuffer);
     blit_vertex_array = create_vao();
 }
 
@@ -424,6 +422,7 @@ draw_cells_interleaved(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen) {
 static void
 draw_cells_interleaved_premult(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen, OSWindow *os_window) {
     if (!os_window->offscreen_texture_id) {
+        glGenFramebuffers(1, &os_window->offscreen_framebuffer);
         glGenTextures(1, &os_window->offscreen_texture_id);
         glBindTexture(GL_TEXTURE_2D, os_window->offscreen_texture_id);
         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, os_window->viewport_width, os_window->viewport_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
@@ -433,7 +432,7 @@ draw_cells_interleaved_premult(ssize_t vao_idx, ssize_t gvao_idx, Screen *screen
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     }
     glBindTexture(GL_TEXTURE_2D, 0);
-    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, offscreen_framebuffer);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, os_window->offscreen_framebuffer);
     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);
diff --git a/kitty/state.c b/kitty/state.c
index 04a37d53b..df83e0ecf 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -255,6 +255,7 @@ destroy_os_window_item(OSWindow *w) {
     }
     Py_CLEAR(w->window_title); Py_CLEAR(w->tab_bar_render_data.screen);
     if (w->offscreen_texture_id) free_texture(&w->offscreen_texture_id);
+    if (w->offscreen_framebuffer) free_framebuffer(&w->offscreen_framebuffer);
     remove_vao(w->tab_bar_render_data.vao_idx);
     remove_vao(w->gvao_idx);
     free(w->tabs); w->tabs = NULL;
diff --git a/kitty/state.h b/kitty/state.h
index 5600dfe67..5ea22b4ff 100644
--- a/kitty/state.h
+++ b/kitty/state.h
@@ -131,6 +131,7 @@ typedef struct {
 typedef struct {
     void *handle;
     id_type id;
+    uint32_t offscreen_framebuffer;
     OSWindowGeometry before_fullscreen;
     int viewport_width, viewport_height, window_width, window_height;
     double viewport_x_ratio, viewport_y_ratio;
@@ -221,6 +222,7 @@ void draw_cells(ssize_t, ssize_t, float, float, float, float, Screen *, OSWindow
 void draw_centered_alpha_mask(OSWindow *w, size_t screen_width, size_t screen_height, size_t width, size_t height, uint8_t *canvas);
 void update_surface_size(int, int, uint32_t);
 void free_texture(uint32_t*);
+void free_framebuffer(uint32_t*);
 void send_image_to_gpu(uint32_t*, const void*, int32_t, int32_t, bool, bool);
 void send_sprite_to_gpu(FONTS_DATA_HANDLE fg, unsigned int, unsigned int, unsigned int, pixel*);
 void blank_canvas(float, color_type);