vo_gpu: opengl: use R8/RG8 formats on GLES 2.0 and GL 2.1

GLES 2.0 contexts with GL_EXT_texture_rg never used single- and
two-component R/RG textures, because the format table only listed
them for GL 3.0/ES 3.0, or for GL 2.1 with texture_rg + texture_float
+ FBOs all present (F_GL2F). Video planes were uploaded as LUMINANCE/
LUMINANCE_ALPHA instead, which needs a swizzle hack and mismatches
the .rg layout produced by dmabuf imports of DRM_FORMAT_R8/GR88
(NV12 via drm-prime), and forced dumb mode due to the have_texrg
check.

Add format classes for ES2 with GL_EXT_texture_rg (unsized internal
formats, as ES2 requires) and for GL 2.1 with ARB/EXT_texture_rg
alone, without the float/FBO requirements of F_GL2F. The entries are
placed before the legacy LUMINANCE ones so format lookups prefer
them; F_GL2RG is suppressed when F_GL2F is active to avoid duplicate
entries.

Author: anarsoul

video/out/opengl/formats.c

@@ -24,6 +24,15 @@ const struct gl_format gl_formats[] = {
     // Specifically not color-renderable.
     {"rgb16",   GL_RGB16,    GL_RGB,             T_U16, F_TF | F_EXT16},
 
+    // GL 2.1 with GL_ARB/EXT_texture_rg, but without requiring FBOs or float
+    // textures (unlike F_GL2F). Upload/filtering only.
+    {"r8",      GL_R8,       GL_RED,             T_U8,  F_TF | F_GL2RG},
+    {"rg8",     GL_RG8,      GL_RG,              T_U8,  F_TF | F_GL2RG},
+
+    // ES2 with GL_EXT_texture_rg. ES2 requires unsized internal formats.
+    {"r",       GL_RED,      GL_RED,             T_U8,  F_TF | F_ES2RG},
+    {"rg",      GL_RG,       GL_RG,              T_U8,  F_TF | F_ES2RG},
+
     // GL2 legacy. Ignores possibly present FBO extensions (no CF flag set).
     {"l8",    GL_LUMINANCE8, GL_LUMINANCE,       T_U8,  F_TF | F_GL2},
     {"la8", GL_LUMINANCE8_ALPHA8, GL_LUMINANCE_ALPHA, T_U8,  F_TF | F_GL2},
@@ -104,7 +113,7 @@ const struct gl_format gl_formats[] = {
 // Return an or-ed combination of all F_ flags that apply.
 int gl_format_feature_flags(GL *gl)
 {
-    return (gl->version == 210 ? F_GL2 : 0)
+    int flags = (gl->version == 210 ? F_GL2 : 0)
          | (gl->version >= 300 ? F_GL3 : 0)
          | (gl->es == 200 ? F_ES2 : 0)
          | (gl->es >= 300 ? F_ES3 : 0)
@@ -116,7 +125,15 @@ int gl_format_feature_flags(GL *gl)
             (gl->mpgl_caps & MPGL_CAP_ARB_FLOAT) &&
             (gl->mpgl_caps & MPGL_CAP_TEX_RG) &&
             (gl->mpgl_caps & MPGL_CAP_FB)) ? F_GL2F : 0)
+         | ((gl->version == 210 &&
+            (gl->mpgl_caps & MPGL_CAP_TEX_RG)) ? F_GL2RG : 0)
+         | ((gl->es == 200 &&
+            (gl->mpgl_caps & MPGL_CAP_TEX_RG)) ? F_ES2RG : 0)
          | (gl->mpgl_caps & MPGL_CAP_APPLE_RGB_422 ? F_APPL : 0);
+    // F_GL2RG is a subset of F_GL2F; avoid duplicate format entries.
+    if (flags & F_GL2F)
+        flags &= ~F_GL2RG;
+    return flags;
 }
 
 int gl_format_type(const struct gl_format *format)

video/out/opengl/formats.h

@@ -25,6 +25,8 @@ enum {
     F_EXTF16    = 1 << 6, // GL_EXT_color_buffer_half_float
     F_GL2F      = 1 << 7, // GL2.1-only with texture_rg + texture_float + FBOs
     F_APPL      = 1 << 8, // GL_APPLE_rgb_422
+    F_GL2RG     = 1 << 9, // GL2.1-only with texture_rg (no float/FBO requirement)
+    F_ES2RG     = 1 << 10, // ES2-only with GL_EXT_texture_rg
 
     // Feature flags. They are additional and signal presence of features.
     F_CR        = 1 << 16, // color-renderable