capabilities testing for fade/ffmpeg

README.md

@@ -264,6 +264,12 @@ unsigned notcurses_supported_styles(const struct notcurses* nc);
 // there is no color support. Note that several terminal emulators advertise
 // more colors than they actually support, downsampling internally.
 int notcurses_palette_size(const struct notcurses* nc);
+
+// Can we fade? Fading requires either the "rgb" or "ccc" terminfo capability.
+bool notcurses_canfade(const struct notcurses* nc);
+
+// Can we load images/videos? This requires being built against FFmpeg.
+bool notcurses_canopen(const struct notcurses* nc);
 ```
 
 ### Input

include/notcurses.h

@@ -330,6 +330,14 @@ API unsigned notcurses_supported_styles(const struct notcurses* nc);
 // more colors than they actually support, downsampling internally.
 API int notcurses_palette_size(const struct notcurses* nc);
 
+// Capabilities
+
+// Can we fade? Fading requires either the "rgb" or "ccc" terminfo capability.
+API bool notcurses_canfade(const struct notcurses* nc);
+
+// Can we load images/videos? This requires being built against FFmpeg.
+API bool notcurses_canopen(const struct notcurses* nc);
+
 typedef struct ncstats {
   uint64_t renders;          // number of successful notcurses_render() runs
   uint64_t failed_renders;   // number of aborted renders, should be 0

src/lib/libav.c

@@ -33,6 +33,10 @@ void ncvisual_destroy(ncvisual* ncv){
 }
 
 #ifndef DISABLE_FFMPEG
+bool notcurses_canopen(const notcurses* nc __attribute__ ((unused))){
+  return true;
+}
+
 static ncvisual*
 ncvisual_create(void){
   ncvisual* ret = malloc(sizeof(*ret));
@@ -400,6 +404,9 @@ int ncvisual_init(void){
 }
 #else
 // built without ffmpeg
+bool notcurses_canopen(const notcurses* nc __attribute__ ((unused))){
+  return false;
+}
 
 struct AVFrame* ncvisual_decode(ncvisual* nc, int* averr){
   (void)nc;

src/lib/notcurses.c

@@ -1598,3 +1598,7 @@ int notcurses_mouse_disable(notcurses* n){
                    /*SET_FOCUS_EVENT_MOUSE ";" */SET_SGR_MODE_MOUSE "l",
                    n->ttyfp, true);
 }
+
+bool notcurses_canfade(const notcurses* nc){
+  return nc->CCCflag || nc->RGBflag;
+}

tests/fade.cpp

@@ -15,6 +15,9 @@ class FadeTest : public :: testing::Test {
     ASSERT_NE(nullptr, outfp_);
     nc_ = notcurses_init(&nopts, outfp_);
     ASSERT_NE(nullptr, nc_);
+    if(!notcurses_canfade(nc_)){
+      GTEST_SKIP();
+    }
     n_ = notcurses_stdplane(nc_);
     ASSERT_NE(nullptr, n_);
     ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 0, 0));

tests/libav.cpp

@@ -2,10 +2,6 @@
 #include "version.h"
 #include "main.h"
 
-#ifndef DISABLE_FFMPEG
-#include <libavutil/pixdesc.h>
-#include <libavutil/avconfig.h>
-#include <libavcodec/avcodec.h> // ffmpeg doesn't reliably "C"-guard itself
 class LibavTest : public :: testing::Test {
  protected:
   void SetUp() override {
@@ -38,6 +34,19 @@ class LibavTest : public :: testing::Test {
   FILE* outfp_{};
 };
 
+#ifdef DISABLE_FFMPEG
+TEST_F(LibavTest, LibavDisabled){
+  ASSERT_FALSE(notcurses_canopen(nc_);
+}
+#else
+#include <libavutil/pixdesc.h>
+#include <libavutil/avconfig.h>
+#include <libavcodec/avcodec.h> // ffmpeg doesn't reliably "C"-guard itself
+
+TEST_F(LibavTest, LibavEnabled){
+  ASSERT_TRUE(notcurses_canopen(nc_));
+}
+
 TEST_F(LibavTest, LoadImage) {
   int averr;
   int dimy, dimx;