terminal/grdev: provide front and back buffer to renderers

We really want more sophisticated aging than just 64bit integers. So
always provide front *and* back buffers to renderers so they can compare
arbitrary aging information and decide whether to re-render.

src/libsystemd-terminal/grdev.c

@@ -343,7 +343,7 @@ void grdev_display_disable(grdev_display *display) {
         }
 }
 
-const grdev_display_target *grdev_display_next_target(grdev_display *display, const grdev_display_target *prev, uint64_t minage) {
+const grdev_display_target *grdev_display_next_target(grdev_display *display, const grdev_display_target *prev) {
         grdev_display_cache *cache;
         size_t idx;
 
@@ -374,26 +374,19 @@ const grdev_display_target *grdev_display_next_target(grdev_display *display, co
                 if (!pipe->running || !pipe->enabled)
                         continue;
 
-                /* if front-buffer is up-to-date, there's nothing to do */
-                if (minage > 0 && pipe->front && pipe->front->age >= minage)
-                        continue;
-
                 /* find suitable back-buffer */
-                if (!(fb = pipe->back)) {
-                        if (!pipe->vtable->target || !(fb = pipe->vtable->target(pipe)))
+                if (!pipe->back) {
+                        if (!pipe->vtable->target)
+                                continue;
+                        if (!(fb = pipe->vtable->target(pipe)))
                                 continue;
 
                         assert(fb == pipe->back);
                 }
 
-                /* if back-buffer is up-to-date, schedule flip */
-                if (minage > 0 && fb->age >= minage) {
-                        grdev_display_flip_target(display, target, fb->age);
-                        continue;
-                }
+                target->front = pipe->front;
+                target->back = pipe->back;
 
-                /* we have an out-of-date back-buffer; return for redraw */
-                target->fb = fb;
                 return target;
         }
 
@@ -408,7 +401,7 @@ void grdev_display_flip_target(grdev_display *display, const grdev_display_targe
         assert(!display->modified);
         assert(display->enabled);
         assert(target);
-        assert(target->fb);
+        assert(target->back);
 
         cache = container_of(target, grdev_display_cache, target);
 
@@ -416,12 +409,12 @@ void grdev_display_flip_target(grdev_display *display, const grdev_display_targe
         assert(cache->pipe->tile->display == display);
 
         /* reset age of all FB on overflow */
-        if (age < target->fb->age)
+        if (age < target->back->age)
                 for (i = 0; i < cache->pipe->max_fbs; ++i)
                         if (cache->pipe->fbs[i])
                                 cache->pipe->fbs[i]->age = 0;
 
-        ((grdev_fb*)target->fb)->age = age;
+        ((grdev_fb*)target->back)->age = age;
         cache->pipe->flip = true;
 }
 

src/libsystemd-terminal/grdev.h

@@ -105,7 +105,8 @@ struct grdev_display_target {
         uint32_t height;
         unsigned int rotate;
         unsigned int flip;
-        const grdev_fb *fb;
+        const grdev_fb *front;
+        const grdev_fb *back;
 };
 
 void grdev_display_set_userdata(grdev_display *display, void *userdata);
@@ -119,13 +120,13 @@ bool grdev_display_is_enabled(grdev_display *display);
 void grdev_display_enable(grdev_display *display);
 void grdev_display_disable(grdev_display *display);
 
-const grdev_display_target *grdev_display_next_target(grdev_display *display, const grdev_display_target *prev, uint64_t minage);
+const grdev_display_target *grdev_display_next_target(grdev_display *display, const grdev_display_target *prev);
 void grdev_display_flip_target(grdev_display *display, const grdev_display_target *target, uint64_t age);
 
-#define GRDEV_DISPLAY_FOREACH_TARGET(_display, _t, _minage)                     \
-        for ((_t) = grdev_display_next_target((_display), NULL, (_minage));     \
-             (_t);                                                              \
-             (_t) = grdev_display_next_target((_display), (_t), (_minage)))
+#define GRDEV_DISPLAY_FOREACH_TARGET(_display, _t)                      \
+        for ((_t) = grdev_display_next_target((_display), NULL);        \
+             (_t);                                                      \
+             (_t) = grdev_display_next_target((_display), (_t)))
 
 /*
  * Events

src/libsystemd-terminal/modeset.c

@@ -234,18 +234,18 @@ static void modeset_draw(Modeset *m, const grdev_display_target *t) {
         uint32_t j, k, *b;
         uint8_t *l;
 
-        assert(t->fb->format == DRM_FORMAT_XRGB8888 || t->fb->format == DRM_FORMAT_ARGB8888);
+        assert(t->back->format == DRM_FORMAT_XRGB8888 || t->back->format == DRM_FORMAT_ARGB8888);
         assert(!t->rotate);
         assert(!t->flip);
 
-        l = t->fb->maps[0];
+        l = t->back->maps[0];
         for (j = 0; j < t->height; ++j) {
                 for (k = 0; k < t->width; ++k) {
                         b = (uint32_t*)l;
                         b[k] = (0xff << 24) | (m->r << 16) | (m->g << 8) | m->b;
                 }
 
-                l += t->fb->strides[0];
+                l += t->back->strides[0];
         }
 }
 
@@ -256,7 +256,7 @@ static void modeset_render(Modeset *m, grdev_display *d) {
         m->g = next_color(&m->g_up, m->g, 3);
         m->b = next_color(&m->b_up, m->b, 2);
 
-        GRDEV_DISPLAY_FOREACH_TARGET(d, t, 0) {
+        GRDEV_DISPLAY_FOREACH_TARGET(d, t) {
                 modeset_draw(m, t);
                 grdev_display_flip_target(d, t, 1);
         }