qml6glsink: add support for texture-target external-oes

In order to use oes-external, the qml6glsink needs a fragment shader that uses
the samplerExternalOES.

The qsb tool is not able to handle shaders that contain samplerExternalOES since
this feature is not supported by all target shading languages. The qsb tool is
able to replace a shader in the qsb file to handle this use case. Use it to
generate a shader variant that uses samplerExternalOES for OpenGL ES and select
that variant if the qml6glsink negotiated texture target oes-external.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7319>

subprojects/gst-plugins-good/ext/qt6/RGBA_gles.frag

@@ -0,0 +1,31 @@
+#version 100
+#extension GL_OES_EGL_image_external : require
+precision highp float;
+precision highp int;
+
+struct buf
+{
+    mat4 qt_Matrix;
+    ivec4 swizzle;
+    mat4 color_matrix;
+    float qt_Opacity;
+};
+
+uniform buf ubuf;
+
+uniform samplerExternalOES tex;
+
+varying vec2 vTexCoord;
+
+vec4 swizzle(vec4 texel, ivec4 swizzle_1)
+{
+    return vec4(texel[swizzle_1.x], texel[swizzle_1.y], texel[swizzle_1.z], texel[swizzle_1.w]);
+}
+
+void main()
+{
+    vec4 param = texture2D(tex, vTexCoord);
+    ivec4 param_1 = ubuf.swizzle;
+    vec4 texel = swizzle(param, param_1);
+    gl_FragData[0] = texel * ubuf.qt_Opacity;
+}

subprojects/gst-plugins-good/ext/qt6/gstqml6glsink.cc

@@ -115,7 +115,8 @@ GST_STATIC_PAD_TEMPLATE ("sink",
     "width = " GST_VIDEO_SIZE_RANGE ", "
     "height = " GST_VIDEO_SIZE_RANGE ", "
     "framerate = " GST_VIDEO_FPS_RANGE ", "
-    "texture-target = (string) 2D"));
+    "texture-target = (string) { " GST_GL_TEXTURE_TARGET_2D_STR ", "
+                                   GST_GL_TEXTURE_TARGET_EXTERNAL_OES_STR " } "));
 
 #define DEFAULT_FORCE_ASPECT_RATIO  TRUE
 #define DEFAULT_PAR_N               0

subprojects/gst-plugins-good/ext/qt6/gstqsg6material.cc

@@ -281,7 +281,10 @@ GstQSGMaterialShader::GstQSGMaterialShader(GstVideoFormat v_format,
     case GST_VIDEO_FORMAT_RGBA:
     case GST_VIDEO_FORMAT_BGRA:
     case GST_VIDEO_FORMAT_RGB:
-      frag_shader = ":/org/freedesktop/gstreamer/qml6/RGBA.frag.qsb";
+      if (target == GST_GL_TEXTURE_TARGET_EXTERNAL_OES)
+        frag_shader = ":/org/freedesktop/gstreamer/qml6/RGBA.frag.qsb.external";
+      else
+        frag_shader = ":/org/freedesktop/gstreamer/qml6/RGBA.frag.qsb";
       break;
     case GST_VIDEO_FORMAT_YV12:
       frag_shader = ":/org/freedesktop/gstreamer/qml6/YUV_TRIPLANAR.frag.qsb";

subprojects/gst-plugins-good/ext/qt6/meson.build

@@ -19,10 +19,10 @@ moc_headers = [
 ]
 
 shader_sources = [
-  'vertex.vert',
-  'RGBA.frag',
-  'YUV_BIPLANAR.frag',
-  'YUV_TRIPLANAR.frag',
+  { 'glsl': 'vertex.vert' },
+  { 'glsl': 'RGBA.frag', '100es': 'RGBA_gles.frag'},
+  { 'glsl': 'YUV_BIPLANAR.frag' },
+  { 'glsl': 'YUV_TRIPLANAR.frag' },
 ]
 
 qt6qml_dep = dependency('', required: false)
@@ -66,6 +66,7 @@ qsb = find_program('qsb-qt6', 'qsb', dirs: [qt6_bindir], required: qt6_option)
 if not qsb.found()
   subdir_done()
 endif
+qsb_wrapper = find_program('qsb-wrapper.py')
 
 optional_deps = []
 qt_defines = []
@@ -167,7 +168,8 @@ if qt6_option.require(have_qt_windowing, error_message: 'No windowing, enable on
   moc_files = qt6_mod.preprocess(moc_headers : moc_headers, method: qt6_method)
   # TODO: dist backup qsb shaders?
   shaders = []
-  foreach shader: shader_sources
+  foreach shader_source: shader_sources
+    shader = shader_source['glsl']
     qsb_shader = shader + '.qsb'
     dist_shader = shader + '-dist.qsb'
 
@@ -177,6 +179,18 @@ if qt6_option.require(have_qt_windowing, error_message: 'No windowing, enable on
       command: [qsb, '--glsl=100 es,120,330', '--batchable', '--output', '@OUTPUT@', '@INPUT@']
     )
     shaders += [compiled_shader]
+
+    if '100es' in shader_source
+      qsb_shader_external = shader + '.qsb.external'
+
+      compiled_shader_external = custom_target(qsb_shader_external,
+        input: [compiled_shader, shader_source['100es']],
+        output: qsb_shader_external,
+        command: [qsb_wrapper, qsb, '@OUTPUT@', '@INPUT1@', '@INPUT0@'],
+      )
+
+      shaders += [compiled_shader_external]
+    endif
   endforeach
   resource_file = configure_file(input: 'resources.qrc', output: 'resources.qrc', copy: true)
   qresources = qt6_mod.compile_resources(sources: resource_file, method: qt6_method)

subprojects/gst-plugins-good/ext/qt6/qsb-wrapper.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+# GStreamer
+# Copyright (C) 2024 Michael Tretter <m.tretter@pengutronix.de>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Library General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Library General Public License for more details.
+#
+# You should have received a copy of the GNU Library General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+#
+
+import shutil
+import subprocess
+import sys
+
+assert (len(sys.argv) == 5)
+
+qsb_tool = sys.argv[1]
+qsb_output = sys.argv[2]
+gles_shader = sys.argv[3]
+qsb_input = sys.argv[4]
+
+# Copy the qsb file since the qsb tool replaces the shader in place
+shutil.copyfile(qsb_input, qsb_output)
+
+subprocess.run([qsb_tool,
+                '--silent',
+                '--replace', 'glsl,100es,{}'.format(gles_shader),
+                qsb_output])

subprojects/gst-plugins-good/ext/qt6/resources.qrc

@@ -1,6 +1,7 @@
 <RCC>
     <qresource prefix="/org/freedesktop/gstreamer/qml6">
         <file>vertex.vert.qsb</file>
+        <file>RGBA.frag.qsb.external</file>
         <file>RGBA.frag.qsb</file>
         <file>YUV_BIPLANAR.frag.qsb</file>
         <file>YUV_TRIPLANAR.frag.qsb</file>