Shaders: ye, SwiftShader, thanks for reminding me of the harsh reality.

256 vectors in total is really damn low, guess I'll have to optimize the
remaining uniform structures to deduplicate the redundant material info.

src/Magnum/Shaders/Test/DistanceFieldVectorGLTest.cpp

@@ -156,7 +156,9 @@ constexpr struct {
     {"classic fallback", {}, 1, 1},
     {"", DistanceFieldVectorGL2D::Flag::UniformBuffers, 1, 1},
     {"texture transformation", DistanceFieldVectorGL2D::Flag::UniformBuffers|DistanceFieldVectorGL2D::Flag::TextureTransformation, 1, 1},
-    {"multiple materials, draws", DistanceFieldVectorGL2D::Flag::UniformBuffers, 64, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-draw is 4+1 in 3D case
+       and 3+1 in 2D, per-material 4 */
+    {"multiple materials, draws", DistanceFieldVectorGL2D::Flag::UniformBuffers, 16, 48},
 };
 
 constexpr struct {

src/Magnum/Shaders/Test/FlatGLTest.cpp

@@ -199,7 +199,9 @@ constexpr struct {
 } ConstructUniformBuffersData[]{
     {"classic fallback", {}, 1},
     {"", FlatGL2D::Flag::UniformBuffers, 1},
-    {"multiple draws", FlatGL2D::Flag::UniformBuffers, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-draw is 4+2 in 3D case
+       and 3+2 in 2D */
+    {"multiple draws", FlatGL2D::Flag::UniformBuffers, 42},
     {"texture transformation", FlatGL2D::Flag::UniformBuffers|FlatGL2D::Flag::Textured|FlatGL2D::Flag::TextureTransformation, 1},
     {"alpha mask", FlatGL2D::Flag::UniformBuffers|FlatGL2D::Flag::AlphaMask, 1},
     {"object ID", FlatGL2D::Flag::UniformBuffers|FlatGL2D::Flag::ObjectId, 1}

src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp

@@ -215,7 +215,9 @@ constexpr struct {
 } ConstructUniformBuffersData2D[] {
     {"classic fallback", MeshVisualizerGL2D::Flag::Wireframe|MeshVisualizerGL2D::Flag::NoGeometryShader, 1, 1},
     {"", MeshVisualizerGL2D::Flag::UniformBuffers|MeshVisualizerGL2D::Flag::Wireframe|MeshVisualizerGL2D::Flag::NoGeometryShader, 1, 1},
-    {"multiple materials, draws", MeshVisualizerGL2D::Flag::UniformBuffers|MeshVisualizerGL2D::Flag::Wireframe|MeshVisualizerGL2D::Flag::NoGeometryShader, 64, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-2D-draw is 4,
+       per-material 4, two need to be left for drawOffset + viewportSize */
+    {"multiple materials, draws", MeshVisualizerGL2D::Flag::UniformBuffers|MeshVisualizerGL2D::Flag::Wireframe|MeshVisualizerGL2D::Flag::NoGeometryShader, 8, 55},
     /* The rest is basically a copy of ConstructData2D with UniformBuffers
        added */
     #ifndef MAGNUM_TARGET_WEBGL
@@ -271,7 +273,9 @@ constexpr struct {
 } ConstructUniformBuffersData3D[] {
     {"classic fallback", MeshVisualizerGL3D::Flag::Wireframe|MeshVisualizerGL3D::Flag::NoGeometryShader, 1, 1},
     {"", MeshVisualizerGL3D::Flag::UniformBuffers|MeshVisualizerGL3D::Flag::Wireframe|MeshVisualizerGL3D::Flag::NoGeometryShader, 1, 1},
-    {"multiple materials, draws", MeshVisualizerGL3D::Flag::UniformBuffers|MeshVisualizerGL3D::Flag::Wireframe|MeshVisualizerGL3D::Flag::NoGeometryShader, 64, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-3D-draw is 4+4,
+       per-material 4, plus 4 for projection */
+    {"multiple materials, draws", MeshVisualizerGL3D::Flag::UniformBuffers|MeshVisualizerGL3D::Flag::Wireframe|MeshVisualizerGL3D::Flag::NoGeometryShader, 6, 28},
     /* The rest is basically a copy of ConstructData2D with UniformBuffers
        added */
     #ifndef MAGNUM_TARGET_WEBGL

src/Magnum/Shaders/Test/PhongGLTest.cpp

@@ -218,8 +218,10 @@ constexpr struct {
 } ConstructUniformBuffersData[]{
     {"classic fallback", {}, 1, 1, 1},
     {"", PhongGL::Flag::UniformBuffers, 1, 1, 1},
-    {"multiple lights, materials, draws", PhongGL::Flag::UniformBuffers, 30, 64, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-3D-draw is 4+4,
-    {"zero lights", PhongGL::Flag::UniformBuffers, 0, 64, 128},
+       per-material 4, per-light 4 plus 4 for projection */
+    {"multiple lights, materials, draws", PhongGL::Flag::UniformBuffers, 8, 8, 24},
+    {"zero lights", PhongGL::Flag::UniformBuffers, 0, 16, 24},
     {"ambient + diffuse + specular texture", PhongGL::Flag::UniformBuffers|PhongGL::Flag::AmbientTexture|PhongGL::Flag::DiffuseTexture|PhongGL::Flag::SpecularTexture, 1, 1, 1},
     {"ambient + diffuse + specular texture + texture transformation", PhongGL::Flag::UniformBuffers|PhongGL::Flag::AmbientTexture|PhongGL::Flag::DiffuseTexture|PhongGL::Flag::SpecularTexture|PhongGL::Flag::TextureTransformation, 1, 1, 1},
     {"normal texture", PhongGL::Flag::UniformBuffers|PhongGL::Flag::NormalTexture, 1, 1, 1},

src/Magnum/Shaders/Test/VectorGLTest.cpp

@@ -155,7 +155,9 @@ constexpr struct {
     {"classic fallback", {}, 1},
     {"", VectorGL2D::Flag::UniformBuffers, 1},
     {"texture transformation", VectorGL2D::Flag::UniformBuffers|VectorGL2D::Flag::TextureTransformation, 1},
-    {"multiple draws", VectorGL2D::Flag::UniformBuffers, 128},
+    /* SwiftShader has 256 uniform vectors at most, per-draw is 4+3 in 3D case
+       and 3+3 in 2D */
+    {"multiple draws", VectorGL2D::Flag::UniformBuffers, 36},
 };
 #endif
 

src/Magnum/Shaders/Test/VertexColorGLTest.cpp

@@ -132,7 +132,9 @@ constexpr struct {
 } ConstructUniformBuffersData[]{
     {"classic fallback", {}, 1},
     {"", VertexColorGL2D::Flag::UniformBuffers, 1},
-    {"multiple draws", VertexColorGL2D::Flag::UniformBuffers, 128}
+    /* SwiftShader has 256 uniform vectors at most, per-draw is 4 in 3D case
+       and 3 in 2D; one needs to be reserved for drawOffset */
+    {"multiple draws", VertexColorGL2D::Flag::UniformBuffers, 63}
 };
 #endif