Correctly render flipped/rotated screens

src/main.c

@@ -347,6 +347,21 @@ static inline void color_to_float_array(GtkStyleContext *ctx,
   out[3] = color.alpha;
 }
 
+static unsigned form_get_rotation(GtkWidget *form) {
+  GtkBuilder *builder = GTK_BUILDER(g_object_get_data(G_OBJECT(form), "builder"));
+  unsigned rot;
+  for (rot = 0; rot < NUM_ROTATIONS; rot++) {
+    GtkWidget *rotate = GTK_WIDGET(gtk_builder_get_object(builder,
+          ROTATE_IDS[rot]));
+    gboolean selected;
+    g_object_get(rotate, "active", &selected, NULL);
+    if (selected) {
+      return rot;
+    }
+  }
+  return -1;
+}
+
 static void queue_canvas_draw(struct wd_state *state) {
   GtkStyleContext *style_ctx = gtk_widget_get_style_context(state->canvas);
   color_to_float_array(style_ctx,
@@ -379,6 +394,13 @@ static void queue_canvas_draw(struct wd_state *state) {
         wl_list_insert(&state->render.heads, &head->render->link);
       }
       struct wd_render_head_data *render = head->render;
+      render->queued.rotation = form_get_rotation(GTK_WIDGET(form_iter->data));
+      if (render->queued.rotation & 1) {
+        int tmp = w;
+        w = h;
+        h = tmp;
+      }
+      render->queued.x_invert = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(gtk_builder_get_object(builder, "flipped")));
       render->x1 = floor(x * state->zoom - state->render.scroll_x - state->render.x_origin);
       render->y1 = floor(y * state->zoom - state->render.scroll_y - state->render.y_origin);
       render->x2 = floor(render->x1 + w * state->zoom / scale);
@@ -839,6 +861,10 @@ static void canvas_render(GtkGLArea *area, GdkGLContext *context, gpointer data)
           render->y_invert = frame->y_invert;
           render->swap_rgb = frame->swap_rgb;
         }
+        if (render->preview) {
+          render->active.rotation = render->queued.rotation;
+          render->active.x_invert = render->queued.x_invert;
+        }
       } else if (render->preview
           || render->pixels == NULL || size_changed(render)) {
         render->tex_width = render->x2 - render->x1;
@@ -852,6 +878,8 @@ static void canvas_render(GtkGLArea *area, GdkGLContext *context, gpointer data)
         render->pixels = cairo_image_surface_get_data(head->surface);
         render->tex_stride = cairo_image_surface_get_stride(head->surface);
         render->updated_at = tick;
+        render->active.rotation = 0;
+        render->active.x_invert = false;
         render->y_invert = false;
         render->swap_rgb = false;
       }

src/render.c

@@ -253,20 +253,39 @@ void wd_gl_render(struct wd_gl_data *res, struct wd_render_data *info,
   int i = 0;
   wl_list_for_each_reverse(head, &info->heads, link) {
     float *tri_ptr = res->tris + i * BT_UV_QUAD_SIZE;
-    float x1 = head->x1;
-    float y1 = head->y1;
-    float x2 = head->x2;
-    float y2 = head->y2;
+    float x1 = head->active.x_invert ? head->x2 : head->x1;
+    float y1 = head->y_invert ? head->y2 : head->y1;
+    float x2 = head->active.x_invert ? head->x1 : head->x2;
+    float y2 = head->y_invert ? head->y1 : head->y2;
 
-    float t1 = head->y_invert ? 1.f : 0.f;
-    float t2 = head->y_invert ? 0.f : 1.f;
+    float sa = 0.f;
+    float sb = 1.f;
+    float sc = sb;
+    float sd = sa;
+    float ta = 0.f;
+    float tb = ta;
+    float tc = 1.f;
+    float td = tc;
+    for (int i = 0; i < head->active.rotation; i++) {
+      float tmp = sd;
+      sd = sc;
+      sc = sb;
+      sb = sa;
+      sa = tmp;
 
-    PUSH_POINT_UV(tri_ptr, x1, y1, 0.f, t1)
-    PUSH_POINT_UV(tri_ptr, x2, y1, 1.f, t1)
-    PUSH_POINT_UV(tri_ptr, x1, y2, 0.f, t2)
-    PUSH_POINT_UV(tri_ptr, x1, y2, 0.f, t2)
-    PUSH_POINT_UV(tri_ptr, x2, y1, 1.f, t1)
-    PUSH_POINT_UV(tri_ptr, x2, y2, 1.f, t2)
+      tmp = td;
+      td = tc;
+      tc = tb;
+      tb = ta;
+      ta = tmp;
+    }
+
+    PUSH_POINT_UV(tri_ptr, x1, y1, sa, ta)
+    PUSH_POINT_UV(tri_ptr, x2, y1, sb, tb)
+    PUSH_POINT_UV(tri_ptr, x1, y2, sd, td)
+    PUSH_POINT_UV(tri_ptr, x1, y2, sd, td)
+    PUSH_POINT_UV(tri_ptr, x2, y1, sb, tb)
+    PUSH_POINT_UV(tri_ptr, x2, y2, sc, tc)
 
     tris += 6;
     i++;

src/wdisplays.h

@@ -148,25 +148,33 @@ struct wd_head {
 
 struct wd_gl_data;
 
+struct wd_render_head_flags {
+  uint8_t rotation;
+  bool x_invert;
+};
+
 struct wd_render_head_data {
   struct wl_list link;
+  uint64_t updated_at;
+  uint64_t transition_begin;
 
   float x1;
   float y1;
   float x2;
   float y2;
 
+  struct wd_render_head_flags queued;
+  struct wd_render_head_flags active;
+
   uint8_t *pixels;
   unsigned tex_stride;
   unsigned tex_width;
   unsigned tex_height;
+
   bool preview;
   bool y_invert;
   bool swap_rgb;
-  uint64_t updated_at;
-
   bool hovered;
-  uint64_t transition_begin;
 };
 
 struct wd_render_data {