[core] Dynamic program compilation for data-driven properties

19 files changed, 148 insertions, 69 deletions

diff --git a/include/mbgl/map/map.hpp b/include/mbgl/map/map.hpp
index 8072eda7dd..bbeeeac6cc 100644
--- a/include/mbgl/map/map.hpp
+++ b/include/mbgl/map/map.hpp
@@ -44,7 +44,7 @@ public:
                  GLContextMode contextMode = GLContextMode::Unique,
                  ConstrainMode constrainMode = ConstrainMode::HeightOnly,
                  ViewportMode viewportMode = ViewportMode::Default,
-                 const std::string& programCacheDir = "");
+                 const optional<std::string>& programCacheDir = {});
     ~Map();
 
     // Register a callback that will get called (on the render thread) when all resources have
diff --git a/src/mbgl/gl/program.hpp b/src/mbgl/gl/program.hpp
index c36543839c..47ad39de7c 100644
--- a/src/mbgl/gl/program.hpp
+++ b/src/mbgl/gl/program.hpp
@@ -50,7 +50,8 @@ public:
                                  const char* vertexSource_,
                                  const char* fragmentSource_) {
 #if MBGL_HAS_BINARY_PROGRAMS
-        if (!programParameters.cacheDir.empty() && context.supportsProgramBinaries()) {
+        optional<std::string> cachePath = programParameters.cachePath(name);
+        if (cachePath && context.supportsProgramBinaries()) {
             const std::string vertexSource =
                 shaders::vertexSource(programParameters, vertexSource_);
             const std::string fragmentSource =
@@ -58,10 +59,8 @@ public:
             const std::string identifier =
                 shaders::programIdentifier(vertexSource, fragmentSource_);
 
-            const std::string cachePath = programParameters.cachePath(name);
-
             try {
-                if (auto cachedBinaryProgram = util::readFile(cachePath)) {
+                if (auto cachedBinaryProgram = util::readFile(*cachePath)) {
                     const BinaryProgram binaryProgram(std::move(*cachedBinaryProgram));
                     if (binaryProgram.identifier() == identifier) {
                         return Program { context, binaryProgram };
@@ -82,8 +81,8 @@ public:
             try {
                 if (const auto binaryProgram =
                         result.template get<BinaryProgram>(context, identifier)) {
-                    util::write_file(cachePath, binaryProgram->serialize());
-                    Log::Warning(Event::OpenGL, "Caching program in: %s", cachePath.c_str());
+                    util::write_file(*cachePath, binaryProgram->serialize());
+                    Log::Warning(Event::OpenGL, "Caching program in: %s", (*cachePath).c_str());
                 }
             } catch (std::runtime_error& error) {
                 Log::Warning(Event::OpenGL, "Failed to cache program: %s", error.what());
diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 181370dc14..35457f3a5b 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -58,7 +58,7 @@ public:
          GLContextMode,
          ConstrainMode,
          ViewportMode,
-         const std::string& programCacheDir);
+         optional<std::string> programCacheDir);
 
     void onSourceChanged(style::Source&) override;
     void onUpdate(Update) override;
@@ -83,7 +83,7 @@ public:
     const MapMode mode;
     const GLContextMode contextMode;
     const float pixelRatio;
-    const std::string programCacheDir;
+    const optional<std::string> programCacheDir;
 
     MapDebugOptions debugOptions { MapDebugOptions::NoDebug };
 
@@ -116,7 +116,7 @@ Map::Map(Backend& backend,
          GLContextMode contextMode,
          ConstrainMode constrainMode,
          ViewportMode viewportMode,
-         const std::string& programCacheDir)
+         const optional<std::string>& programCacheDir)
     : impl(std::make_unique<Impl>(*this,
                                   backend,
                                   pixelRatio,
@@ -139,7 +139,7 @@ Map::Impl::Impl(Map& map_,
                 GLContextMode contextMode_,
                 ConstrainMode constrainMode_,
                 ViewportMode viewportMode_,
-                const std::string& programCacheDir_)
+                optional<std::string> programCacheDir_)
     : map(map_),
       observer(backend_),
       backend(backend_),
diff --git a/src/mbgl/programs/program.hpp b/src/mbgl/programs/program.hpp
index 420d2e1397..bbe4885745 100644
--- a/src/mbgl/programs/program.hpp
+++ b/src/mbgl/programs/program.hpp
@@ -9,18 +9,21 @@
 #include <mbgl/shaders/shaders.hpp>
 #include <mbgl/util/io.hpp>
 
+#include <unordered_map>
+
 namespace mbgl {
 
 template <class Shaders,
           class Primitive,
           class LayoutAttrs,
           class Uniforms,
-          class PaintProperties>
+          class PaintProps>
 class Program {
 public:
     using LayoutAttributes = LayoutAttrs;
     using LayoutVertex = typename LayoutAttributes::Vertex;
 
+    using PaintProperties = PaintProps;
     using PaintPropertyBinders = typename PaintProperties::Binders;
     using PaintAttributes = typename PaintPropertyBinders::Attributes;
     using Attributes = gl::ConcatenateAttributes<LayoutAttributes, PaintAttributes>;
@@ -71,4 +74,34 @@ public:
     }
 };
 
+template <class Program>
+class ProgramMap {
+public:
+    using PaintProperties = typename Program::PaintProperties;
+    using PaintPropertyBinders = typename Program::PaintPropertyBinders;
+    using Bitset = typename PaintPropertyBinders::Bitset;
+
+    ProgramMap(gl::Context& context_, ProgramParameters parameters_)
+        : context(context_),
+          parameters(std::move(parameters_)) {
+    }
+
+    Program& get(const typename PaintProperties::Evaluated& currentProperties) {
+        Bitset bits = PaintPropertyBinders::constants(currentProperties);
+        auto it = programs.find(bits);
+        if (it != programs.end()) {
+            return it->second;
+        }
+        return programs.emplace(std::piecewise_construct,
+                                std::forward_as_tuple(bits),
+                                std::forward_as_tuple(context,
+                                    parameters.withAdditionalDefines(PaintPropertyBinders::defines(currentProperties)))).first->second;
+    }
+
+private:
+    gl::Context& context;
+    ProgramParameters parameters;
+    std::unordered_map<Bitset, Program> programs;
+};
+
 } // namespace mbgl
diff --git a/src/mbgl/programs/program_parameters.cpp b/src/mbgl/programs/program_parameters.cpp
index f9f680ac1e..e76ec4be71 100644
--- a/src/mbgl/programs/program_parameters.cpp
+++ b/src/mbgl/programs/program_parameters.cpp
@@ -7,7 +7,7 @@ namespace mbgl {
 
 ProgramParameters::ProgramParameters(const float pixelRatio,
                                      const bool overdraw,
-                                     std::string cacheDir_)
+                                     optional<std::string> cacheDir_)
     : defines([&] {
           std::ostringstream ss;
           ss.imbue(std::locale("C"));
@@ -18,15 +18,31 @@ ProgramParameters::ProgramParameters(const float pixelRatio,
           }
           return ss.str();
       }()),
-      hash(std::hash<std::string>()(defines)),
       cacheDir(std::move(cacheDir_)) {
 }
 
-std::string ProgramParameters::cachePath(const char* name) const {
-    std::ostringstream ss;
-    ss << cacheDir << "/com.mapbox.gl.shader." << name << "." << std::setfill('0')
-       << std::setw(sizeof(size_t) * 2) << std::hex << hash << ".pbf";
-    return ss.str();
+const std::string& ProgramParameters::getDefines() const {
+    return defines;
+}
+
+optional<std::string> ProgramParameters::cachePath(const char* name) const {
+    if (!cacheDir) {
+        return {};
+    } else {
+        std::ostringstream ss;
+        ss << *cacheDir << "/com.mapbox.gl.shader." << name << "." << std::setfill('0')
+           << std::setw(sizeof(size_t) * 2) << std::hex << std::hash<std::string>()(defines) << ".pbf";
+        return ss.str();
+    }
+}
+
+ProgramParameters ProgramParameters::withAdditionalDefines(const std::vector<std::string>& additionalDefines) const {
+    ProgramParameters result(*this);
+    for (const auto& define : additionalDefines) {
+        result.defines += define;
+        result.defines += "\n";
+    }
+    return result;
 }
 
 } // namespace mbgl
diff --git a/src/mbgl/programs/program_parameters.hpp b/src/mbgl/programs/program_parameters.hpp
index 420658d089..e94e61c217 100644
--- a/src/mbgl/programs/program_parameters.hpp
+++ b/src/mbgl/programs/program_parameters.hpp
@@ -1,20 +1,24 @@
 #pragma once
 
+#include <mbgl/util/optional.hpp>
+
 #include <string>
+#include <vector>
 
 namespace mbgl {
 
 class ProgramParameters {
 public:
-    ProgramParameters(float pixelRatio, bool overdraw, std::string cacheDir);
+    ProgramParameters(float pixelRatio, bool overdraw, optional<std::string> cacheDir);
 
-    const std::string defines;
+    const std::string& getDefines() const;
+    optional<std::string> cachePath(const char* name) const;
 
-    std::string cachePath(const char* name) const;
+    ProgramParameters withAdditionalDefines(const std::vector<std::string>& defines) const;
 
 private:
-    const std::size_t hash;
-    const std::string cacheDir;
+    std::string defines;
+    optional<std::string> cacheDir;
 };
 
 } // namespace mbgl
diff --git a/src/mbgl/programs/programs.hpp b/src/mbgl/programs/programs.hpp
index b58d2e3bee..37ced32745 100644
--- a/src/mbgl/programs/programs.hpp
+++ b/src/mbgl/programs/programs.hpp
@@ -35,21 +35,21 @@ public:
           collisionBox(context, programParameters) {
     }
 
-    CircleProgram circle;
+    ProgramMap<CircleProgram> circle;
     ExtrusionTextureProgram extrusionTexture;
-    FillProgram fill;
-    FillExtrusionProgram fillExtrusion;
-    FillExtrusionPatternProgram fillExtrusionPattern;
-    FillPatternProgram fillPattern;
-    FillOutlineProgram fillOutline;
-    FillOutlinePatternProgram fillOutlinePattern;
-    LineProgram line;
-    LineSDFProgram lineSDF;
-    LinePatternProgram linePattern;
+    ProgramMap<FillProgram> fill;
+    ProgramMap<FillExtrusionProgram> fillExtrusion;
+    ProgramMap<FillExtrusionPatternProgram> fillExtrusionPattern;
+    ProgramMap<FillPatternProgram> fillPattern;
+    ProgramMap<FillOutlineProgram> fillOutline;
+    ProgramMap<FillOutlinePatternProgram> fillOutlinePattern;
+    ProgramMap<LineProgram> line;
+    ProgramMap<LineSDFProgram> lineSDF;
+    ProgramMap<LinePatternProgram> linePattern;
     RasterProgram raster;
-    SymbolIconProgram symbolIcon;
-    SymbolSDFIconProgram symbolIconSDF;
-    SymbolSDFTextProgram symbolGlyph;
+    ProgramMap<SymbolIconProgram> symbolIcon;
+    ProgramMap<SymbolSDFIconProgram> symbolIconSDF;
+    ProgramMap<SymbolSDFTextProgram> symbolGlyph;
 
     DebugProgram debug;
     CollisionBoxProgram collisionBox;
diff --git a/src/mbgl/programs/symbol_program.hpp b/src/mbgl/programs/symbol_program.hpp
index 1b7232c9e4..01e95f456d 100644
--- a/src/mbgl/programs/symbol_program.hpp
+++ b/src/mbgl/programs/symbol_program.hpp
@@ -324,7 +324,7 @@ template <class Shaders,
           class Primitive,
           class LayoutAttrs,
           class Uniforms,
-          class PaintProperties>
+          class PaintProps>
 class SymbolProgram {
 public:
     using LayoutAttributes = LayoutAttrs;
@@ -332,6 +332,7 @@ public:
     
     using LayoutAndSizeAttributes = gl::ConcatenateAttributes<LayoutAttributes, SymbolSizeAttributes>;
 
+    using PaintProperties = PaintProps;
     using PaintPropertyBinders = typename PaintProperties::Binders;
     using PaintAttributes = typename PaintPropertyBinders::Attributes;
     using Attributes = gl::ConcatenateAttributes<LayoutAndSizeAttributes, PaintAttributes>;
diff --git a/src/mbgl/renderer/paint_property_binder.hpp b/src/mbgl/renderer/paint_property_binder.hpp
index a4bea24bbf..062b77888e 100644
--- a/src/mbgl/renderer/paint_property_binder.hpp
+++ b/src/mbgl/renderer/paint_property_binder.hpp
@@ -6,6 +6,8 @@
 #include <mbgl/util/type_list.hpp>
 #include <mbgl/renderer/paint_property_statistics.hpp>
 
+#include <bitset>
+
 namespace mbgl {
 
 /*
@@ -54,8 +56,7 @@ std::array<float, N*2> zoomInterpolatedAttributeValue(const std::array<float, N>
 
    * For _constant_ properties -- those whose value is a constant, or the constant
      result of evaluating a camera function at a particular camera position -- we
-     don't need a vertex buffer, and can instead use a constant attribute binding
-     via the `glVertexAttrib*` family of functions.
+     don't need a vertex buffer, and instead use a uniform.
    * For source functions, we use a vertex buffer with a single attribute value,
      the evaluated result of the source function for the given feature.
    * For composite functions, we use a vertex buffer with two attributes: min and
@@ -66,15 +67,8 @@ std::array<float, N*2> zoomInterpolatedAttributeValue(const std::array<float, N>
      between the min and max value at the final displayed zoom level. The use of a
      uniform allows us to cheaply update the value on every frame.
 
-   Note that the shader source is the same regardless of the strategy used to bind
-   the attribute -- in all cases the attribute is declared as a vec2, in order to
-   support composite min and max values (color attributes use a vec4 with special
-   packing). When the constant or source function strategies are used, the
-   interpolation uniform value is set to zero, and the second attribute element is
-   unused. This differs from the GL JS implementation, which dynamically generates
-   shader source based on the strategy used. We found that in WebGL, using
-   `glVertexAttrib*` was unnacceptably slow. Additionally, in GL Native we have
-   implemented binary shader caching, which works better if the shaders are constant.
+   Note that the shader source varies depending on whether we're using a uniform or
+   attribute. Like GL JS, we dynamically compile shaders at runtime to accomodate this.
 */
 template <class T, class A>
 class PaintPropertyBinder {
@@ -170,9 +164,13 @@ public:
         return 0.0f;
     }
 
-    T uniformValue(const PossiblyEvaluatedPropertyValue<T>&) const override {
-        // Uniform values for vertex attribute arrays are unused.
-        return {};
+    T uniformValue(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
+        if (currentValue.isConstant()) {
+            return *currentValue.constant();
+        } else {
+            // Uniform values for vertex attribute arrays are unused.
+            return {};
+        }
     }
 
 private:
@@ -230,9 +228,13 @@ public:
         return util::interpolationFactor(1.0f, std::get<0>(coveringRanges), currentZoom);
     }
 
-    T uniformValue(const PossiblyEvaluatedPropertyValue<T>&) const override {
-        // Uniform values for vertex attribute arrays are unused.
-        return {};
+    T uniformValue(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
+        if (currentValue.isConstant()) {
+            return *currentValue.constant();
+        } else {
+            // Uniform values for vertex attribute arrays are unused.
+            return {};
+        }
     }
 
 private:
@@ -342,6 +344,30 @@ public:
         return binders.template get<P>()->statistics;
     }
 
+
+    using Bitset = std::bitset<sizeof...(Ps)>;
+
+    template <class EvaluatedProperties>
+    static Bitset constants(const EvaluatedProperties& currentProperties) {
+        Bitset result;
+        util::ignore({
+            result.set(TypeIndex<Ps, Ps...>::value,
+                       currentProperties.template get<Ps>().isConstant())...
+        });
+        return result;
+    }
+
+    template <class EvaluatedProperties>
+    static std::vector<std::string> defines(const EvaluatedProperties& currentProperties) {
+        std::vector<std::string> result;
+        util::ignore({
+            (result.push_back(currentProperties.template get<Ps>().isConstant()
+                ? std::string("#define HAS_UNIFORM_") + Ps::Uniform::name()
+                : std::string()), 0)...
+        });
+        return result;
+    }
+
 private:
     Binders binders;
 };
diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index eed3bfcd8b..da4903864b 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -93,7 +93,7 @@ static gl::VertexVector<ExtrusionTextureLayoutVertex> extrusionTextureVertices()
 Painter::Painter(gl::Context& context_,
                  const TransformState& state_,
                  float pixelRatio,
-                 const std::string& programCacheDir)
+                 const optional<std::string>& programCacheDir)
     : context(context_),
       state(state_),
       tileVertexBuffer(context.createVertexBuffer(tileVertices())),
diff --git a/src/mbgl/renderer/painter.hpp b/src/mbgl/renderer/painter.hpp
index 47b469d971..4658f0c206 100644
--- a/src/mbgl/renderer/painter.hpp
+++ b/src/mbgl/renderer/painter.hpp
@@ -74,7 +74,7 @@ struct FrameData {
 
 class Painter : private util::noncopyable {
 public:
-    Painter(gl::Context&, const TransformState&, float pixelRatio, const std::string& programCacheDir);
+    Painter(gl::Context&, const TransformState&, float pixelRatio, const optional<std::string>& programCacheDir);
     ~Painter();
 
     void render(const style::Style&,
diff --git a/src/mbgl/renderer/painter_background.cpp b/src/mbgl/renderer/painter_background.cpp
index 7cd9cbac5f..d01696ee3e 100644
--- a/src/mbgl/renderer/painter_background.cpp
+++ b/src/mbgl/renderer/painter_background.cpp
@@ -33,7 +33,7 @@ void Painter::renderBackground(PaintParameters& parameters, const RenderBackgrou
         spriteAtlas->bind(true, context, 0);
 
         for (const auto& tileID : util::tileCover(state, state.getIntegerZoom())) {
-            parameters.programs.fillPattern.draw(
+            parameters.programs.fillPattern.get(properties).draw(
                 context,
                 gl::Triangles(),
                 depthModeForSublayer(0, gl::DepthMode::ReadOnly),
@@ -58,7 +58,7 @@ void Painter::renderBackground(PaintParameters& parameters, const RenderBackgrou
         }
     } else {
         for (const auto& tileID : util::tileCover(state, state.getIntegerZoom())) {
-            parameters.programs.fill.draw(
+            parameters.programs.fill.get(properties).draw(
                 context,
                 gl::Triangles(),
                 depthModeForSublayer(0, gl::DepthMode::ReadOnly),
diff --git a/src/mbgl/renderer/painter_circle.cpp b/src/mbgl/renderer/painter_circle.cpp
index 7c9194f6dd..13acb5f7fe 100644
--- a/src/mbgl/renderer/painter_circle.cpp
+++ b/src/mbgl/renderer/painter_circle.cpp
@@ -23,7 +23,7 @@ void Painter::renderCircle(PaintParameters& parameters,
     const CirclePaintProperties::Evaluated& properties = layer.evaluated;
     const bool scaleWithMap = properties.get<CirclePitchScale>() == CirclePitchScaleType::Map;
 
-    parameters.programs.circle.draw(
+    parameters.programs.circle.get(properties).draw(
         context,
         gl::Triangles(),
         depthModeForSublayer(0, gl::DepthMode::ReadOnly),
diff --git a/src/mbgl/renderer/painter_clipping.cpp b/src/mbgl/renderer/painter_clipping.cpp
index 0d3b5f1504..b3a2d77b1a 100644
--- a/src/mbgl/renderer/painter_clipping.cpp
+++ b/src/mbgl/renderer/painter_clipping.cpp
@@ -8,7 +8,7 @@ namespace mbgl {
 void Painter::renderClippingMask(const UnwrappedTileID& tileID, const ClipID& clip) {
     static const style::FillPaintProperties::Evaluated properties {};
     static const FillProgram::PaintPropertyBinders paintAttibuteData(properties, 0);
-    programs->fill.draw(
+    programs->fill.get(properties).draw(
         context,
         gl::Triangles(),
         gl::DepthMode::disabled(),
diff --git a/src/mbgl/renderer/painter_fill.cpp b/src/mbgl/renderer/painter_fill.cpp
index 622f6386ef..e1b59d8839 100644
--- a/src/mbgl/renderer/painter_fill.cpp
+++ b/src/mbgl/renderer/painter_fill.cpp
@@ -38,7 +38,7 @@ void Painter::renderFill(PaintParameters& parameters,
                          const auto& drawMode,
                          const auto& indexBuffer,
                          const auto& segments) {
-            program.draw(
+            program.get(properties).draw(
                 context,
                 drawMode,
                 depthModeForSublayer(sublayer, gl::DepthMode::ReadWrite),
@@ -85,7 +85,7 @@ void Painter::renderFill(PaintParameters& parameters,
                          const auto& drawMode,
                          const auto& indexBuffer,
                          const auto& segments) {
-            program.draw(
+            program.get(properties).draw(
                 context,
                 drawMode,
                 depthModeForSublayer(sublayer, gl::DepthMode::ReadWrite),
diff --git a/src/mbgl/renderer/painter_fill_extrusion.cpp b/src/mbgl/renderer/painter_fill_extrusion.cpp
index af98cae569..95617525c7 100644
--- a/src/mbgl/renderer/painter_fill_extrusion.cpp
+++ b/src/mbgl/renderer/painter_fill_extrusion.cpp
@@ -36,7 +36,7 @@ void Painter::renderFillExtrusion(PaintParameters& parameters,
 
         spriteAtlas->bind(true, context, 0);
 
-        parameters.programs.fillExtrusionPattern.draw(
+        parameters.programs.fillExtrusionPattern.get(properties).draw(
             context,
             gl::Triangles(),
             depthModeForSublayer(0, gl::DepthMode::ReadWrite),
@@ -62,7 +62,7 @@ void Painter::renderFillExtrusion(PaintParameters& parameters,
             state.getZoom());
 
     } else {
-        parameters.programs.fillExtrusion.draw(
+        parameters.programs.fillExtrusion.get(properties).draw(
             context,
             gl::Triangles(),
             depthModeForSublayer(0, gl::DepthMode::ReadWrite),
diff --git a/src/mbgl/renderer/painter_line.cpp b/src/mbgl/renderer/painter_line.cpp
index 4d7a27d0f6..9152ac8512 100644
--- a/src/mbgl/renderer/painter_line.cpp
+++ b/src/mbgl/renderer/painter_line.cpp
@@ -24,7 +24,7 @@ void Painter::renderLine(PaintParameters& parameters,
     const LinePaintProperties::Evaluated& properties = layer.evaluated;
 
     auto draw = [&] (auto& program, auto&& uniformValues) {
-        program.draw(
+        program.get(properties).draw(
             context,
             gl::Triangles(),
             depthModeForSublayer(0, gl::DepthMode::ReadOnly),
diff --git a/src/mbgl/renderer/painter_symbol.cpp b/src/mbgl/renderer/painter_symbol.cpp
index 5a66d1e62f..86b2146b9f 100644
--- a/src/mbgl/renderer/painter_symbol.cpp
+++ b/src/mbgl/renderer/painter_symbol.cpp
@@ -41,7 +41,7 @@ void Painter::renderSymbol(PaintParameters& parameters,
         // We clip symbols to their tile extent in still mode.
         const bool needsClipping = frame.mapMode == MapMode::Still;
 
-        program.draw(
+        program.get(paintProperties).draw(
             context,
             gl::Triangles(),
             values_.pitchAlignment == AlignmentType::Map
diff --git a/src/mbgl/shaders/shaders.cpp b/src/mbgl/shaders/shaders.cpp
index 93e273f985..31ff405f02 100644
--- a/src/mbgl/shaders/shaders.cpp
+++ b/src/mbgl/shaders/shaders.cpp
@@ -10,11 +10,11 @@ namespace mbgl {
 namespace shaders {
 
 std::string fragmentSource(const ProgramParameters& parameters, const char* fragmentSource) {
-    return parameters.defines + fragmentPrelude + fragmentSource;
+    return parameters.getDefines() + fragmentPrelude + fragmentSource;
 }
 
 std::string vertexSource(const ProgramParameters& parameters, const char* vertexSource) {
-    return parameters.defines + vertexPrelude + vertexSource;
+    return parameters.getDefines() + vertexPrelude + vertexSource;
 }
 
 std::string programIdentifier(const std::string& vertexSource, const std::string& fragmentSource) {