opengl: infer fbo format name in gl_fb_query

src/opengl/gpu_tex.c

@@ -460,6 +460,56 @@ pl_tex gl_tex_create(pl_gpu gpu, const struct pl_tex_params *params)
     return NULL;
 }
 
+struct fmt_mapping {
+    const char *name;
+    GLenum format;
+    GLenum type;
+};
+
+// taken from OpenGL 4.6 Spec table 8.27
+static const struct fmt_mapping fmt_mappings[] = {
+    {"rgba32f", GL_RGBA, GL_FLOAT},
+    {"rgba16f", GL_RGBA, GL_HALF_FLOAT},
+    {"rg32f", GL_RG, GL_FLOAT},
+    {"rg16f", GL_RG, GL_HALF_FLOAT},
+    {"r11f_g11f_b10f", GL_RGB, GL_UNSIGNED_INT_10F_11F_11F_REV},
+    {"r32f", GL_RED, GL_FLOAT},
+    {"r16f", GL_RED, GL_HALF_FLOAT},
+    {"rgba32ui", GL_RGBA_INTEGER, GL_UNSIGNED_INT},
+    {"rgba16ui", GL_RGBA_INTEGER, GL_UNSIGNED_SHORT},
+    {"rgb10_a2ui", GL_RGBA_INTEGER, GL_UNSIGNED_INT_2_10_10_10_REV},
+    {"rgba8ui", GL_RGBA_INTEGER, GL_UNSIGNED_BYTE},
+    {"rg32ui", GL_RG_INTEGER, GL_UNSIGNED_INT},
+    {"rg16ui", GL_RG_INTEGER, GL_UNSIGNED_SHORT},
+    {"rg8ui", GL_RG_INTEGER, GL_UNSIGNED_BYTE},
+    {"r32ui", GL_RED_INTEGER, GL_UNSIGNED_INT},
+    {"r16ui", GL_RED_INTEGER, GL_UNSIGNED_SHORT},
+    {"r8ui", GL_RED_INTEGER, GL_UNSIGNED_BYTE},
+    {"rgba32i", GL_RGBA_INTEGER, GL_INT},
+    {"rgba16i", GL_RGBA_INTEGER, GL_SHORT},
+    {"rgba8i", GL_RGBA_INTEGER, GL_BYTE},
+    {"rg32i", GL_RG_INTEGER, GL_INT},
+    {"rg16i", GL_RG_INTEGER, GL_SHORT},
+    {"rg8i", GL_RG_INTEGER, GL_BYTE},
+    {"r32i", GL_RED_INTEGER, GL_INT},
+    {"r16i", GL_RED_INTEGER, GL_SHORT},
+    {"r8", GL_RED_INTEGER, GL_BYTE},
+    {"rgba16", GL_RGBA, GL_UNSIGNED_SHORT},
+    {"rgb10_a2", GL_RGBA, GL_UNSIGNED_INT_2_10_10_10_REV},
+    {"rgba8", GL_RGBA, GL_UNSIGNED_BYTE},
+    {"rg16", GL_RG, GL_UNSIGNED_SHORT},
+    {"rg8", GL_RG, GL_UNSIGNED_BYTE},
+    {"r16", GL_RED, GL_UNSIGNED_SHORT},
+    {"r8", GL_RED, GL_UNSIGNED_BYTE},
+    {"rgba16_snorm", GL_RGBA, GL_SHORT},
+    {"rgba8_snorm", GL_RGBA, GL_BYTE},
+    {"rg16_snorm", GL_RG, GL_SHORT},
+    {"rg8_snorm", GL_RG, GL_BYTE},
+    {"r16_snorm", GL_RED, GL_SHORT},
+    {"r8_snorm", GL_RED, GL_BYTE},
+    {NULL, 0, 0}
+};
+
 static bool gl_fb_query(pl_gpu gpu, int fbo, struct pl_fmt_t *fmt,
                         struct gl_format *glfmt)
 {
@@ -489,7 +539,7 @@ static bool gl_fb_query(pl_gpu gpu, int fbo, struct pl_fmt_t *fmt,
         if (fbo != 0)
             obj = GL_COLOR_ATTACHMENT0;
 
-        GLint type = 0;
+        GLint format = 0, type = 0;
         gl->GetFramebufferAttachmentParameteriv(GL_DRAW_FRAMEBUFFER, obj,
                             GL_FRAMEBUFFER_ATTACHMENT_COMPONENT_TYPE, &type);
         switch (type) {
@@ -510,6 +560,21 @@ static bool gl_fb_query(pl_gpu gpu, int fbo, struct pl_fmt_t *fmt,
         gl->GetFramebufferAttachmentParameteriv(GL_DRAW_FRAMEBUFFER, obj,
                 GL_FRAMEBUFFER_ATTACHMENT_ALPHA_SIZE, &fmt->component_depth[3]);
 
+        if (p->gl_ver >= 45) {
+            // Try to infer the format name.
+            // We could use GetTexLevelParameter to query the internal format
+            // but it requires obtaining the texture using ARB_multi_bind or ARB_direct_state_access.
+            // So instead we infer it using read format and type.
+            gl->GetFramebufferParameteriv(GL_DRAW_FRAMEBUFFER, GL_IMPLEMENTATION_COLOR_READ_FORMAT, &format);
+            gl->GetFramebufferParameteriv(GL_DRAW_FRAMEBUFFER, GL_IMPLEMENTATION_COLOR_READ_TYPE, &type);
+            for (const struct fmt_mapping *f = fmt_mappings; f->name; f++) {
+                if (format == f->format && type == f->type) {
+                    fmt->name = f->name;
+                    break;
+                }
+            }
+        }
+
         gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
         gl_check_err(gpu, "gl_fb_query");