Add an option to downscale hi-res views

Some older devices that use gpu_unai don't have a high enough
resolution to display all of the pixels in high-res mode. There's a
setting in unai to skip rendering of these pixels, but it's not
connected to the libretro frontend, and does not appear to be used in
the gpulib implementation at all.

This commit adds a gpu_unai setting, Enable Hi-Res Downscaling, that
will enable pixel skipping and blit only the pixels actually rendered
into a buffer no larger than 384x240. This buffer is then treated as
the actual framebuffer by gpulib and the libretro frontend.

2 files changed, 16 insertions, 0 deletions

diff --git a/plugins/gpulib/gpu.h b/plugins/gpulib/gpu.h
index 7e1d18b..009297d 100644
--- a/plugins/gpulib/gpu.h
+++ b/plugins/gpulib/gpu.h
@@ -68,6 +68,8 @@ struct psx_gpu {
     uint32_t blanked:1;
     uint32_t enhancement_enable:1;
     uint32_t enhancement_active:1;
+    uint32_t downscale_enable:1;
+    uint32_t downscale_active:1;
     uint32_t *frame_count;
     uint32_t *hcnt; /* hsync count */
     struct {
@@ -91,6 +93,8 @@ struct psx_gpu {
   int useDithering:1; /* 0 - off , 1 - on */
   uint16_t *(*get_enhancement_bufer)
     (int *x, int *y, int *w, int *h, int *vram_h);
+  uint16_t *(*get_downscale_buffer)
+    (int *x, int *y, int *w, int *h, int *vram_h);
   void *(*mmap)(unsigned int size);
   void  (*munmap)(void *ptr, unsigned int size);
 };
diff --git a/plugins/gpulib/vout_pl.c b/plugins/gpulib/vout_pl.c
index a9437cb..075e3c3 100644
--- a/plugins/gpulib/vout_pl.c
+++ b/plugins/gpulib/vout_pl.c
@@ -43,6 +43,15 @@ static void check_mode_change(int force)
     h_out *= 2;
   }
 
+  gpu.state.downscale_active =
+    gpu.get_downscale_buffer != NULL && gpu.state.downscale_enable
+    && (w >= 512 || h >= 256);
+
+  if (gpu.state.downscale_active) {
+    w_out = w < 512 ? w : 320;
+    h_out = h < 256 ? h : h / 2;
+  }
+
   // width|rgb24 change?
   if (force || (gpu.status.reg ^ old_status) & ((7<<16)|(1<<21)) || h != old_h)
   {
@@ -69,6 +78,9 @@ void vout_update(void)
   if (gpu.state.enhancement_active)
     vram = gpu.get_enhancement_bufer(&x, &y, &w, &h, &vram_h);
 
+  if (gpu.state.downscale_active)
+    vram = gpu.get_downscale_buffer(&x, &y, &w, &h, &vram_h);
+
   if (y + h > vram_h) {
     if (y + h - vram_h > h / 2) {
       // wrap