gfx/caca,fpga: reuse menu frame buffer across set_texture_frame calls

Both drivers unconditionally free'd menu_frame and set it to NULL
before a subsequent size-comparison check, making the
"only reallocate if size changed" branch dead. Every menu frame
triggered a full free+malloc+memcpy round-trip on a buffer that
typically never changes size after the first call.

Replace with a cached-capacity realloc pattern: allocate or grow only
when the required size exceeds the current capacity; otherwise reuse
the existing buffer. On realloc failure the previous frame is kept
intact (the original free+malloc sequence would have lost it).

fpga_gfx.c also had a separate latent bug: the pitch calculation used
fpga->rgb32 (the video/core pixel format) instead of the rgb32 parameter
(the menu pixel format), producing wrong bytes-per-pixel when core and
menu formats differed. The menu_bits assignment had the same bug. Both
fixed to use the incoming parameter.

Thread-safety: set_texture_frame and the frame read-site both run on
the video thread (threaded video) or main thread (non-threaded),
sequentially within the same loop iteration. No synchronization
required, none added. The realloc pattern additionally closes a
transient NULL window that existed between the free and malloc in
the original code.

Author: LibretroAdmin

gfx/drivers/caca_gfx.c

@@ -49,6 +49,7 @@ typedef struct caca
    caca_dither_t *dither;
    caca_display_t *display;
    unsigned char *menu_frame;
+   size_t menu_frame_cap;
    unsigned menu_width;
    unsigned menu_height;
    unsigned menu_pitch;
@@ -371,27 +372,29 @@ static void caca_set_texture_frame(void *data,
       const void *frame, bool rgb32, unsigned width, unsigned height,
       float alpha)
 {
-   caca_t *caca   = (caca_t*)data;
-   unsigned pitch = width * 2;
+   caca_t  *caca    = (caca_t*)data;
+   unsigned pitch   = width * (rgb32 ? 4 : 2);
+   size_t   required;
 
-   if (rgb32)
-      pitch = width * 4;
+   if (!frame || !width || !height || !pitch)
+      return;
 
-   if (caca->menu_frame)
-      free(caca->menu_frame);
-   caca->menu_frame = NULL;
+   required = (size_t)pitch * (size_t)height;
 
-   if (    (!caca->menu_frame)
-         || (caca->menu_width  != width)
-         || (caca->menu_height != height)
-         || (caca->menu_pitch  != pitch))
+   if (required > caca->menu_frame_cap)
    {
-      if (pitch && height)
-         caca->menu_frame = (unsigned char*)malloc(pitch * height);
+      unsigned char *tmp = (unsigned char*)realloc(
+            caca->menu_frame, required);
+      if (!tmp)
+         return;                        /* keep previous frame intact */
+      caca->menu_frame     = tmp;
+      caca->menu_frame_cap = required;
    }
 
-   if (caca->menu_frame && frame && pitch && height)
-      memcpy(caca->menu_frame, frame, pitch * height);
+   memcpy(caca->menu_frame, frame, required);
+   caca->menu_width  = width;
+   caca->menu_height = height;
+   caca->menu_pitch  = pitch;
 }
 
 static const video_poke_interface_t caca_poke_interface = {

gfx/drivers/fpga_gfx.c

@@ -53,6 +53,7 @@ typedef struct fpga
    RegOp regOp; /* ptr alignment */
    volatile unsigned *framebuffer;
    unsigned char *menu_frame;
+   size_t menu_frame_cap;
    unsigned menu_width;
    unsigned menu_height;
    unsigned menu_pitch;
@@ -307,31 +308,30 @@ static void fpga_set_texture_frame(void *data,
       const void *frame, bool rgb32, unsigned width, unsigned height,
       float alpha)
 {
-   fpga_t *fpga   = (fpga_t*)data;
-   unsigned pitch = width * 2;
+   fpga_t  *fpga    = (fpga_t*)data;
+   unsigned pitch   = width * (rgb32 ? 4 : 2);
+   size_t   required;
 
-   if (fpga->rgb32)
-      pitch = width * 4;
-
-   if (fpga->menu_frame)
-      free(fpga->menu_frame);
-   fpga->menu_frame = NULL;
+   if (!frame || !width || !height || !pitch)
+      return;
 
-   if (  !fpga->menu_frame           ||
-         fpga->menu_width  != width  ||
-         fpga->menu_height != height ||
-         fpga->menu_pitch != pitch)
-      if (pitch && height)
-         fpga->menu_frame = (unsigned char*)malloc(pitch * height);
+   required = (size_t)pitch * (size_t)height;
 
-   if (fpga->menu_frame && frame && pitch && height)
+   if (required > fpga->menu_frame_cap)
    {
-      memcpy(fpga->menu_frame, frame, pitch * height);
-      fpga->menu_width  = width;
-      fpga->menu_height = height;
-      fpga->menu_pitch  = pitch;
-      fpga->menu_bits   = fpga->rgb32 ? 32 : 16;
+      unsigned char *tmp = (unsigned char*)realloc(
+            fpga->menu_frame, required);
+      if (!tmp)
+         return;                        /* keep previous frame intact */
+      fpga->menu_frame     = tmp;
+      fpga->menu_frame_cap = required;
    }
+
+   memcpy(fpga->menu_frame, frame, required);
+   fpga->menu_width  = width;
+   fpga->menu_height = height;
+   fpga->menu_pitch  = pitch;
+   fpga->menu_bits   = rgb32 ? 32 : 16;
 }
 
 /* TODO/FIXME - implement */