remove the majority of notcurses_check_pixel_support() calls #1469

NEWS.md

@@ -2,6 +2,15 @@ This document attempts to list user-visible changes and any major internal
 rearrangements of Notcurses.
 
 * 2.3.5 (not yet released)
+  * Happy day! The terminal interrogation routines in the initialization code 
+    have been completely revamped. The first outcome of this is that Sixel
+    parameters are now opportunistically read at startup, and thus there is
+    no longer any need to call `notcurses_check_pixel_support()` before
+    using `NCBLIT_PIXEL`. If it's there, it'll be used; if not, it'll degrade
+    or fail. Indeed, this function will likely be removed for ABI3. The new
+    routines rely on the terminal answering the Send Device Attributes escape;
+    if it does not, Notcurses may refuse to start, or even hang. Please report
+    a bug if you run into this.
   * `CELL_ALPHA_*` macros are now `NCALPHA_*`. The former will remain
     `#define`d until ABI3.
 

README.md

@@ -264,7 +264,7 @@ to breaking under incorrect `TERM` values. If you're not using `xterm`, your
 
 * **Q:** How about *arbitrary image manipulation here* functionality? **A:** I'm not going to beat ImageMagick et al. on image manipulation, but you can load an `ncvisual` from RGBA memory using `ncvisual_from_rgba()`.
 
-* **Q:** My program locks up when I run `notcurses_check_pixel_support()`. **A**: Detecting bitmap support requires interrogating the terminal. If the terminal doesn't reply to standard interrogations, send upstream a patch, or use a different terminal. Generally, only old and unsupported terminal emulators exhibit this behavior.
+* **Q:** My program locks up during initialization. **A**: Notcurses interrogates the terminal. If the terminal doesn't reply to standard interrogations, file a Notcurses bug, send upstream a patch, or use a different terminal. Generally, only old and unsupported terminal emulators exhibit this behavior.
 
 * **Q:** How do I mix Rendered and Direct mode? **A:** You really don't want to. You can stream a subprocess to a plane with the `ncsubproc` widget.
 

USAGE.md

@@ -942,10 +942,8 @@ ncplane_dim_x(const struct ncplane* n){
 
 // Retrieve pixel geometry for the display region ('pxy', 'pxx'), each cell
 // ('celldimy', 'celldimx'), and the maximum displayable bitmap ('maxbmapy',
-// 'maxbmapx'). Note that this will call notcurses_check_pixel_support(),
-// possibly leading to an interrogation of the terminal. If bitmaps are not
-// supported, 'maxbmapy' and 'maxbmapx' will be 0. Any of the geometry
-// arguments may be NULL.
+// 'maxbmapx'). If bitmaps are not supported, 'maxbmapy' and 'maxbmapx' will
+// be 0. Any of the geometry arguments may be NULL.
 void ncplane_pixelgeom(struct ncplane* n, int* restrict pxy, int* restrict pxx,
                        int* restrict celldimy, int* restrict celldimx,
                        int* restrict maxbmapy, int* restrict maxbmapx);

doc/man/man3/notcurses_capabilities.3.md

@@ -87,8 +87,7 @@ quadrants and halfblocks, respectively. **notcurses_canbraille** returns
 these functions return **true** unless UTF-8 encoding is in use.
 
 **notcurses_check_pixel_support** returns 1 if bitmap support (via any
-mechanism) is detected; **NCBLIT_PIXEL** can be used after such a return.
-It returns 0 a lack of bitmap support was confirmed, and -1 on error.
+mechanism) has been detected, and otherwise 0.
 
 # NOTES
 

doc/man/man3/notcurses_plane.3.md

@@ -363,10 +363,7 @@ plane when scrolling is enabled).
 return the size of the plane in pixels. **celldimy** and **celldimx** return
 the size of a cell in pixels (these ought be the same across planes).
 **maxbmapy** and **maxbmapx** describe the largest bitmap which can be
-displayed in the plane. This function transitively calls
-**notcurses_check_pixel_support**, possibly leading to terminal interrogation
-(see **notcurses_capabilities(3)** for why this may be undesirable). Any
-parameter (save **n**) may be **NULL**.
+displayed in the plane. Any parameter (save **n**) may be **NULL**.
 
 When a plane is blitted to using **ncvisual_render** and **NCBLIT_PIXEL** (see
 **notcurses_visual(3)**), it ceases to accept cell-based output. The sprixel

doc/man/man3/notcurses_visual.3.md

@@ -254,14 +254,6 @@ information.
 # PIXEL BLITTING
 
 Some terminals support pixel-based output via one of a number of protocols.
-Checking for bitmap support requires interrogating the terminal and reading a
-response. This takes time, and will never complete if the terminal doesn't
-respond. Notcurses will not do so without an explicit request from the client
-code. Before **NCBLIT_PIXEL** can be used, it is thus necessary to call
-**notcurses_check_pixel_support**. If this function has not successfully
-returned, attempts to use **NCBLIT_PIXEL** will fall back to cell-based
-blitting (or fail, if **NCVISUAL_OPTION_NODEGRADE** is used).
-
 **NCBLIT_PIXEL** has some stringent requirements on the type of planes it can
 be used with; it is usually best to let **ncvisual_render** create the backing
 plane by providing a **NULL** value for **n**. If you must bring your own

include/notcurses/direct.h

@@ -246,9 +246,7 @@ API bool ncdirect_canopen_images(const struct ncdirect* n)
 API bool ncdirect_canutf8(const struct ncdirect* n)
   __attribute__ ((nonnull (1)));
 
-// This function must successfully return before NCBLIT_PIXEL is available.
-// Returns -1 on error, 0 for no support, or 1 if pixel output is supported.
-// Must not be called concurrently with either input or rasterization.
+// Can we blit pixel-accurate bitmaps?
 API int ncdirect_check_pixel_support(struct ncdirect* n)
   __attribute__ ((nonnull (1)));
 

include/notcurses/notcurses.h

@@ -1122,10 +1122,8 @@ ncplane_dim_x(const struct ncplane* n){
 
 // Retrieve pixel geometry for the display region ('pxy', 'pxx'), each cell
 // ('celldimy', 'celldimx'), and the maximum displayable bitmap ('maxbmapy',
-// 'maxbmapx'). Note that this will call notcurses_check_pixel_support(),
-// possibly leading to an interrogation of the terminal. If bitmaps are not
-// supported, 'maxbmapy' and 'maxbmapx' will be 0. Any of the geometry
-// arguments may be NULL.
+// 'maxbmapx'). If bitmaps are not supported, 'maxbmapy' and 'maxbmapx' will
+// be 0. Any of the geometry arguments may be NULL.
 API void ncplane_pixelgeom(struct ncplane* n, int* RESTRICT pxy, int* RESTRICT pxx,
                            int* RESTRICT celldimy, int* RESTRICT celldimx,
                            int* RESTRICT maxbmapy, int* RESTRICT maxbmapx)
@@ -1292,9 +1290,7 @@ API bool notcurses_cansextant(const struct notcurses* nc)
 API bool notcurses_canbraille(const struct notcurses* nc)
   __attribute__ ((nonnull (1)));
 
-// This function must successfully return before NCBLIT_PIXEL is available.
-// Returns -1 on error, 0 for no support, or 1 if pixel output is supported.
-// Must not be called concurrently with either input or rasterization.
+// Can we blit pixel-accurate bitmaps?
 API int notcurses_check_pixel_support(struct notcurses* nc)
   __attribute__ ((nonnull (1)));
 

src/fetch/main.c

@@ -578,7 +578,6 @@ display_thread(void* vmarshal){
   struct marshal* m = vmarshal;
   drawpalette(m->nc);
   if(ncdirect_canopen_images(m->nc)){
-    ncdirect_check_pixel_support(m->nc);
     if(m->logo){
       if(ncdirect_render_image(m->nc, m->logo, NCALIGN_CENTER,
                                NCBLIT_PIXEL, NCSCALE_SCALE_HIRES) == 0){

src/info/main.c

@@ -37,7 +37,6 @@ int main(void){
   if(nc == NULL){
     return EXIT_FAILURE;
   }
-  notcurses_check_pixel_support(nc);
   notcurses_debug_caps(nc, mstream);
   if(fclose(mstream)){
     notcurses_stop(nc);

src/lib/termdesc.c

@@ -405,7 +405,7 @@ int interrogate_terminfo(tinfo* ti, int fd, const char* termname, unsigned utf8,
   if(ti->color_registers >= 64){
     setup_sixel_bitmaps(ti);
   }
-  if(!nocbreak){
+  if(nocbreak){
     if(fd >= 0){
       if(tcsetattr(fd, TCSANOW, &ti->tpreserved)){
         ncinputlayer_stop(&ti->input);

src/ls/main.cpp

@@ -266,7 +266,6 @@ int main(int argc, char* const * argv){
     blitter,
     scale,
   };
-  ctx.nc.check_pixel_support();
   keep_working = true;
   for(auto s = 0u ; s < procs ; ++s){
     threads.emplace_back(std::thread(ncls_thread, &ctx));