add visual_resize_internal to visual_interface API #1718

NEWS.md

@@ -1,6 +1,10 @@
 This document attempts to list user-visible changes and any major internal
 rearrangements of Notcurses.
 
+* 2.3.3 (not yet released)
+  * `ncvisual_blit()` without a multimedia engine will now properly scale
+    the output according to the provided `ncvisual_options`.
+
 * 2.3.2 (2021-06-03)
   * Fixed a bug affecting certain scalings of `ncvisual` objects created from
     memory (e.g. `ncvisual_from_rgba()`).

src/lib/internal.h

@@ -1649,6 +1649,8 @@ resize_bitmap(const uint32_t* bmap, int srows, int scols, size_t sstride,
   return ret;
 }
 
+// implemented by a multimedia backend (ffmpeg or oiio), and installed
+// prior to calling notcurses_core_init() (by notcurses_init()).
 typedef struct ncvisual_implementation {
   int (*visual_init)(int loglevel);
   void (*visual_printbanner)(const struct notcurses* nc);
@@ -1665,6 +1667,14 @@ typedef struct ncvisual_implementation {
   int (*visual_stream)(notcurses* nc, struct ncvisual* ncv, float timescale,
                        ncstreamcb streamer, const struct ncvisual_options* vopts, void* curry);
   char* (*visual_subtitle)(const struct ncvisual* ncv);
+  // do a resize, without updating the ncvisual structure. if the target
+  // parameters are already matched, the existing data will be returned.
+  // otherwise, a scaled copy will be returned. they can be differentiated
+  // by comparing the result against ncv->data.
+  uint32_t* (*visual_resize_internal)(const struct ncvisual* ncv, int rows,
+                                      int* stride, int cols,
+                                      const struct blitterargs* bargs);
+  // do a persistent resize, changing the ncv itself
   int (*visual_resize)(struct ncvisual* ncv, int rows, int cols);
   void (*visual_destroy)(struct ncvisual* ncv);
   bool canopen_images;

src/media/ffmpeg.c

@@ -631,6 +631,7 @@ static const ncvisual_implementation ffmpeg_impl = {
   .visual_decode_loop = ffmpeg_decode_loop,
   .visual_stream = ffmpeg_stream,
   .visual_subtitle = ffmpeg_subtitle,
+  .visual_resize_internal = ffmpeg_resize_internal,
   .visual_resize = ffmpeg_resize,
   .visual_destroy = ffmpeg_destroy,
   .canopen_images = true,