14 files changed, 99 insertions, 219 deletions

diff --git a/include/llmr/geometry/debug_font_buffer.hpp b/include/llmr/geometry/debug_font_buffer.hpp
index 28a50d372e..15f6daf07f 100644
--- a/include/llmr/geometry/debug_font_buffer.hpp
+++ b/include/llmr/geometry/debug_font_buffer.hpp
@@ -1,26 +1,15 @@
 #ifndef LLMR_GEOMETRY_DEBUG_FONT_BUFFER
 #define LLMR_GEOMETRY_DEBUG_FONT_BUFFER
 
-#include <vector>
-#include <cstdint>
+#include "buffer.hpp"
 
 namespace llmr {
 
-class DebugFontBuffer {
+class DebugFontBuffer : public Buffer<
+    4 // 2 bytes per coordinate, 2 coordinates
+> {
 public:
-    DebugFontBuffer();
-    ~DebugFontBuffer();
-
     void addText(const char *text, double left, double baseline, double scale = 1);
-    void clear();
-
-    uint32_t length();
-    void bind();
-
-private:
-    std::vector<uint16_t> array;
-    uint32_t buffer;
-    bool dirty;
 };
 
 }
diff --git a/include/llmr/geometry/fill_buffer.hpp b/include/llmr/geometry/fill_buffer.hpp
index b141825fcb..f413715042 100644
--- a/include/llmr/geometry/fill_buffer.hpp
+++ b/include/llmr/geometry/fill_buffer.hpp
@@ -1,35 +1,32 @@
 #ifndef LLMR_GEOMETRY_FILL_BUFFER
 #define LLMR_GEOMETRY_FILL_BUFFER
 
+#include "buffer.hpp"
 #include <vector>
 #include <cstdint>
 
 namespace llmr {
 
-class FillBuffer {
+
+class FillVertexBuffer : public Buffer<
+    4 // bytes per coordinates (2 * unsigned short == 4 bytes)
+> {
 public:
     typedef int16_t vertex_type;
-    typedef uint16_t element_type;
-    const uint8_t components = 2;
-
-    FillBuffer();
-    ~FillBuffer();
-
-    uint32_t vertex_length() const;
-    uint32_t elements_length() const;
 
     void addDegenerate();
-    void addCoordinate(vertex_type x, vertex_type y);
-    void addElements(element_type a, element_type b, element_type c);
+    void add(vertex_type x, vertex_type y);
+};
+
 
-    void bind();
+class FillElementsBuffer : public Buffer<
+    6, // bytes per triangle (3 * unsigned short == 6 bytes)
+    GL_ELEMENT_ARRAY_BUFFER
+> {
+public:
+    typedef uint16_t element_type;
 
-private:
-    std::vector<vertex_type> vertices;
-    std::vector<element_type> elements;
-    uint32_t vertex_buffer;
-    uint32_t element_buffer;
-    bool dirty;
+    void add(element_type a, element_type b, element_type c);
 };
 
 }
diff --git a/include/llmr/geometry/line_buffer.hpp b/include/llmr/geometry/line_buffer.hpp
index 412ba860c8..ccbdce1191 100644
--- a/include/llmr/geometry/line_buffer.hpp
+++ b/include/llmr/geometry/line_buffer.hpp
@@ -1,17 +1,16 @@
 #ifndef LLMR_GEOMETRY_LINE_BUFFER
 #define LLMR_GEOMETRY_LINE_BUFFER
 
-#include <vector>
-#include <cstdint>
-#include <cmath>
+#include "buffer.hpp"
 
 namespace llmr {
 
-class LineBuffer {
+
+class LineBuffer : public Buffer<
+    8 // 2 coordinates per vertex + 1 linesofar + 1 extrude coord pair == 4 (== 8 bytes)
+> {
 public:
     typedef int16_t vertex_type;
-    
-    ~LineBuffer();
 
     /*
      * Scale the extrusion vector so that the normal length is this value.
@@ -44,22 +43,6 @@ public:
      * coordinate of the next triangle strip.
      */
     void addDegenerate();
-
-    /*
-     * Returns the number of elements in this buffer. This is not the number of
-     * bytes, but rather the number of coordinates with associated information.
-     */
-    uint32_t length() const;
-
-    /*
-     * Transfers this buffer to the GPU and binds the buffer to the GL context.
-     */
-    void bind();
-
-private:
-    bool dirty = true;
-    std::vector<vertex_type> array;
-    uint32_t buffer = 0;
 };
 
 }
diff --git a/include/llmr/geometry/vertex_buffer.hpp b/include/llmr/geometry/vertex_buffer.hpp
index 5dd5ec7195..9d053693c9 100644
--- a/include/llmr/geometry/vertex_buffer.hpp
+++ b/include/llmr/geometry/vertex_buffer.hpp
@@ -17,7 +17,7 @@ public:
      * Returns the number of elements in this buffer. This is not the number of
      * bytes, but rather the number of coordinates with associated information.
      */
-    uint32_t length() const;
+    uint32_t index() const;
 
     /*
      * Transfers this buffer to the GPU and binds the buffer to the GL context.
diff --git a/include/llmr/map/tile.hpp b/include/llmr/map/tile.hpp
index 7896d91ebd..d0d660a4e6 100644
--- a/include/llmr/map/tile.hpp
+++ b/include/llmr/map/tile.hpp
@@ -21,7 +21,8 @@ class LayerDescription;
 class BucketDescription;
 class VectorTile;
 class VectorTileLayer;
-class FillBuffer;
+class FillVertexBuffer;
+class FillElementsBuffer;
 class LineBuffer;
 class PlainShader;
 
@@ -72,7 +73,8 @@ public:
     DebugFontBuffer debugFontBuffer;
     VertexArrayObject<PlainShader> debugFontArray;
 
-    std::shared_ptr<FillBuffer> fillBuffer;
+    std::shared_ptr<FillVertexBuffer> fillVertexBuffer;
+    std::shared_ptr<FillElementsBuffer> fillElementsBuffer;
     std::shared_ptr<LineBuffer> lineBuffer;
 
     // Holds the buckets of this tile.
diff --git a/include/llmr/renderer/fill_bucket.hpp b/include/llmr/renderer/fill_bucket.hpp
index 209e164e8b..2992d77109 100644
--- a/include/llmr/renderer/fill_bucket.hpp
+++ b/include/llmr/renderer/fill_bucket.hpp
@@ -16,7 +16,8 @@
 namespace llmr {
 
 class Style;
-class FillBuffer;
+class FillVertexBuffer;
+class FillElementsBuffer;
 class BucketDescription;
 class OutlineShader;
 class PlainShader;
@@ -25,7 +26,9 @@ struct pbf;
 
 class FillBucket : public Bucket {
 public:
-    FillBucket(const std::shared_ptr<FillBuffer>& buffer, const BucketDescription& bucket_desc);
+    FillBucket(const std::shared_ptr<FillVertexBuffer>& vertexBuffer,
+               const std::shared_ptr<FillElementsBuffer>& elementsBuffer,
+               const BucketDescription& bucket_desc);
 
     virtual void render(Painter& painter, const std::string& layer_name, const Tile::ID& id);
 
@@ -40,7 +43,8 @@ public:
     const BucketGeometryDescription geom_desc;
 
 private:
-    std::shared_ptr<FillBuffer> buffer;
+    std::shared_ptr<FillVertexBuffer> vertexBuffer;
+    std::shared_ptr<FillElementsBuffer> elementsBuffer;
 
     struct group {
         VertexArrayObject<PlainShader> array;
diff --git a/src/geometry/debug_font_buffer.cpp b/src/geometry/debug_font_buffer.cpp
index 7316ca21cd..4db1aa285a 100644
--- a/src/geometry/debug_font_buffer.cpp
+++ b/src/geometry/debug_font_buffer.cpp
@@ -7,20 +7,9 @@
 
 using namespace llmr;
 
-DebugFontBuffer::DebugFontBuffer()
-    : buffer(0),
-      dirty(true) {
-
-}
-
-DebugFontBuffer::~DebugFontBuffer() {
-    if (buffer != 0) {
-        glDeleteBuffers(1, &buffer);
-        buffer = 0;
-    }
-}
-
 void DebugFontBuffer::addText(const char *text, double left, double baseline, double scale) {
+    uint16_t *coords = nullptr;
+
     int32_t length = strlen(text);
     for (int32_t i = 0; i < length; ++i) {
         if (text[i] < 32 || text[i] > 127) {
@@ -45,39 +34,17 @@ void DebugFontBuffer::addText(const char *text, double left, double baseline, do
                 int16_t x = round(left + glyph.data[j] * scale);
                 int16_t y = round(baseline - glyph.data[j + 1] * scale);
                 if (prev) {
-                    array.push_back(prev_x);
-                    array.push_back(prev_y);
-                    array.push_back(x);
-                    array.push_back(y);
+                    coords = static_cast<uint16_t *>(addElement());
+                    coords[0] = prev_x;
+                    coords[1] = prev_y;
+
+                    coords = static_cast<uint16_t *>(addElement());
+                    coords[0] = x;
+                    coords[1] = y;
                 }
                 prev_x = x; prev_y = y; prev = true;
             }
         }
         left += glyph.width * scale;
     }
-
-    dirty = true;
-}
-
-void DebugFontBuffer::clear() {
-    array.clear();
-    dirty = true;
-}
-
-uint32_t DebugFontBuffer::length() {
-    // We store 2 coordinates per vertex
-    return array.size() / 2;
-}
-
-void DebugFontBuffer::bind() {
-    if (buffer == 0) {
-        glGenBuffers(1, &buffer);
-    }
-
-    glBindBuffer(GL_ARRAY_BUFFER, buffer);
-
-    if (dirty) {
-        glBufferData(GL_ARRAY_BUFFER, array.size() * sizeof(uint16_t), array.data(), GL_STATIC_DRAW);
-        dirty = false;
-    }
 }
diff --git a/src/geometry/fill_buffer.cpp b/src/geometry/fill_buffer.cpp
index a90664238d..3de008a7a7 100644
--- a/src/geometry/fill_buffer.cpp
+++ b/src/geometry/fill_buffer.cpp
@@ -5,65 +5,21 @@
 
 using namespace llmr;
 
-FillBuffer::FillBuffer()
-    : vertex_buffer(0),
-      element_buffer(0),
-      dirty(true) {
-
-}
-
-FillBuffer::~FillBuffer() {
-    if (vertex_buffer != 0) {
-        glDeleteBuffers(1, &vertex_buffer);
-        vertex_buffer = 0;
-    }
-    if (element_buffer != 0) {
-        glDeleteBuffers(1, &element_buffer);
-        element_buffer = 0;
-    }
-}
-
-uint32_t FillBuffer::vertex_length() const {
-    // We store 2 coordinates per vertex
-    return vertices.size() / 2;
-}
-
-uint32_t FillBuffer::elements_length() const {
-    // A triangle has 3 indices
-    return elements.size() / 3;
+void FillVertexBuffer::addDegenerate() {
+    vertex_type *vertices = static_cast<vertex_type *>(addElement());
+    vertices[0] = 32767;
+    vertices[1] = 0;
 }
 
-void FillBuffer::addDegenerate() {
-    vertices.push_back(32767);
-    vertices.push_back(0);
+void FillVertexBuffer::add(vertex_type x, vertex_type y) {
+    vertex_type *vertices = static_cast<vertex_type *>(addElement());
+    vertices[0] = x;
+    vertices[1] = y;
 }
 
-void FillBuffer::addCoordinate(vertex_type x, vertex_type y) {
-    vertices.push_back(x);
-    vertices.push_back(y);
-}
-
-void FillBuffer::addElements(element_type a, element_type b, element_type c) {
-    elements.push_back(a);
-    elements.push_back(b);
-    elements.push_back(c);
-}
-
-void FillBuffer::bind() {
-    if (vertex_buffer == 0) {
-        glGenBuffers(1, &vertex_buffer);
-    }
-
-    if (element_buffer == 0) {
-        glGenBuffers(1, &element_buffer);
-    }
-
-    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_buffer);
-
-    if (dirty) {
-        glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(vertex_type), vertices.data(), GL_STATIC_DRAW);
-        glBufferData(GL_ELEMENT_ARRAY_BUFFER, elements.size() * sizeof(element_type), elements.data(), GL_STATIC_DRAW);
-        dirty = false;
-    }
+void FillElementsBuffer::add(element_type a, element_type b, element_type c) {
+    element_type *elements = static_cast<element_type *>(addElement());
+    elements[0] = a;
+    elements[1] = b;
+    elements[2] = c;
 }
diff --git a/src/geometry/line_buffer.cpp b/src/geometry/line_buffer.cpp
index 4e1200d2f6..b9c770c04a 100644
--- a/src/geometry/line_buffer.cpp
+++ b/src/geometry/line_buffer.cpp
@@ -1,46 +1,23 @@
 #include <llmr/geometry/line_buffer.hpp>
 #include <llmr/platform/gl.hpp>
 
-using namespace llmr;
-
-LineBuffer::~LineBuffer() {
-    if (buffer != 0) {
-        glDeleteBuffers(1, &buffer);
-        buffer = 0;
-    }
-}
+#include <cmath>
 
-uint32_t LineBuffer::length() const {
-    // We store 2 coordinates per vertex + 1 linesofar + 1 extrude coord pair == 4 (== 8 bytes)
-    return array.size() / 4;
-}
+using namespace llmr;
 
 void LineBuffer::add(vertex_type x, vertex_type y, float ex, float ey, int8_t tx, int8_t ty, int32_t linesofar) {
-    array.push_back((x * 2) | tx);
-    array.push_back((y * 2) | ty);
-    array.push_back(linesofar);
+    void *data = addElement();
 
-    int16_t extrude = 0;
-    *(((int8_t *)&extrude) + 0) = round(extrudeScale * ex);
-    *(((int8_t *)&extrude) + 1) = round(extrudeScale * ey);
+    int16_t *coords = static_cast<int16_t *>(data);
+    coords[0] = (x * 2) | tx;
+    coords[1] = (y * 2) | ty;
+    coords[2] = linesofar;
 
-    array.push_back(extrude);
-    if (!dirty) dirty = true;
+    int8_t *extrude = static_cast<int8_t *>(data);
+    extrude[6] = round(extrudeScale * ex);
+    extrude[7] = round(extrudeScale * ey);
 };
 
 void LineBuffer::addDegenerate() {
     add(16383, 16383, 0, 0, 1, 1, 0);
 }
-
-void LineBuffer::bind() {
-    if (buffer == 0) {
-        glGenBuffers(1, &buffer);
-    }
-
-    glBindBuffer(GL_ARRAY_BUFFER, buffer);
-
-    if (dirty) {
-        glBufferData(GL_ARRAY_BUFFER, array.size() * sizeof(vertex_type), array.data(), GL_STATIC_DRAW);
-        dirty = false;
-    }
-}
diff --git a/src/geometry/vertex_buffer.cpp b/src/geometry/vertex_buffer.cpp
index 2d209f6be1..47fe73a2aa 100644
--- a/src/geometry/vertex_buffer.cpp
+++ b/src/geometry/vertex_buffer.cpp
@@ -12,7 +12,7 @@ VertexBuffer::~VertexBuffer() {
     }
 }
 
-uint32_t VertexBuffer::length() const {
+uint32_t VertexBuffer::index() const {
     // We store 2 coordinates per vertex + 1 linesofar + 1 extrude coord pair == 4 (== 8 bytes)
     return array.size() / 2;
 }
diff --git a/src/map/tile.cpp b/src/map/tile.cpp
index da0ad00066..016811af00 100644
--- a/src/map/tile.cpp
+++ b/src/map/tile.cpp
@@ -42,7 +42,8 @@ std::forward_list<Tile::ID> Tile::children(const ID& id, int32_t z) {
 Tile::Tile(ID id, const Style& style)
     : id(id),
       state(initial),
-      fillBuffer(std::make_shared<FillBuffer>()),
+      fillVertexBuffer(std::make_shared<FillVertexBuffer>()),
+      fillElementsBuffer(std::make_shared<FillElementsBuffer>()),
       lineBuffer(std::make_shared<LineBuffer>()),
       style(style) {
 
@@ -166,7 +167,7 @@ std::shared_ptr<Bucket> Tile::createBucket(const VectorTile& tile, const BucketD
 }
 
 std::shared_ptr<Bucket> Tile::createFillBucket(const VectorTileLayer& layer, const BucketDescription& bucket_desc) {
-    std::shared_ptr<FillBucket> bucket = std::make_shared<FillBucket>(fillBuffer, bucket_desc);
+    std::shared_ptr<FillBucket> bucket = std::make_shared<FillBucket>(fillVertexBuffer, fillElementsBuffer, bucket_desc);
 
     FilteredVectorTileLayer filtered_layer(layer, bucket_desc);
     for (pbf feature : filtered_layer) {
diff --git a/src/renderer/fill_bucket.cpp b/src/renderer/fill_bucket.cpp
index bfa50b0079..8446c04f2b 100644
--- a/src/renderer/fill_bucket.cpp
+++ b/src/renderer/fill_bucket.cpp
@@ -14,11 +14,14 @@ struct geometry_too_long_exception : std::exception {};
 
 using namespace llmr;
 
-FillBucket::FillBucket(const std::shared_ptr<FillBuffer>& buffer, const BucketDescription& bucket_desc)
+FillBucket::FillBucket(const std::shared_ptr<FillVertexBuffer>& vertexBuffer,
+                       const std::shared_ptr<FillElementsBuffer>& elementsBuffer,
+                       const BucketDescription& bucket_desc)
     : geom_desc(bucket_desc.geometry),
-      buffer(buffer),
-      vertex_start(buffer->vertex_length()),
-      elements_start(buffer->elements_length()),
+      vertexBuffer(vertexBuffer),
+      elementsBuffer(elementsBuffer),
+      vertex_start(vertexBuffer->index()),
+      elements_start(elementsBuffer->index()),
       length(0) {
 }
 
@@ -44,13 +47,13 @@ void FillBucket::addGeometry(pbf& geom) {
 }
 
 void FillBucket::addGeometry(const std::vector<Coordinate>& line) {
-    uint32_t vertex_start = buffer->vertex_length();
-    buffer->addDegenerate();
+    uint32_t vertex_start = vertexBuffer->index();
+    vertexBuffer->addDegenerate();
     for (const Coordinate& coord : line) {
-        buffer->addCoordinate(coord.x, coord.y);
+        vertexBuffer->add(coord.x, coord.y);
     }
 
-    uint32_t vertex_end = buffer->vertex_length();
+    uint32_t vertex_end = vertexBuffer->index();
 
     if (vertex_end - vertex_start > 65535) {
         throw geometry_too_long_exception();
@@ -78,13 +81,13 @@ void FillBucket::addGeometry(const std::vector<Coordinate>& line) {
 
     assert(firstIndex + vertex_count - 1 < 65536);
 
-    uint32_t elements_start = buffer->elements_length();
+    uint32_t elements_start = elementsBuffer->index();
 
     for (uint32_t i = 2; i < vertex_count; ++i) {
-        buffer->addElements(firstIndex, firstIndex + i - 1, firstIndex + i);
+        elementsBuffer->add(firstIndex, firstIndex + i - 1, firstIndex + i);
     }
 
-    uint32_t elements_end = buffer->elements_length();
+    uint32_t elements_end = elementsBuffer->index();
     uint32_t elements_count = elements_end - elements_start;
     group.vertex_length += vertex_count;
     group.elements_length += elements_count;
@@ -105,7 +108,8 @@ void FillBucket::drawElements(PlainShader& shader) {
     char *vertex_index = BUFFER_OFFSET(vertex_start * 2 * sizeof(int16_t));
     char *elements_index = BUFFER_OFFSET(elements_start * 3 * sizeof(int16_t));
     for (group& group : groups) {
-        group.array.bind(shader, *buffer, vertex_index);
+        group.array.bind(shader, *vertexBuffer, vertex_index);
+        elementsBuffer->bind();
         glDrawElements(GL_TRIANGLES, group.elements_length * 3 - 3, GL_UNSIGNED_SHORT, elements_index);
         vertex_index += group.vertex_length * 2 * sizeof(uint16_t);
         elements_index += group.elements_length * 3 * sizeof(uint16_t);
@@ -115,6 +119,6 @@ void FillBucket::drawElements(PlainShader& shader) {
 void FillBucket::drawVertices(OutlineShader& shader) {
     // Draw the entire line
     char *vertex_index = BUFFER_OFFSET(vertex_start * 2 * sizeof(int16_t));
-    array.bind(shader, *buffer, vertex_index);
+    array.bind(shader, *vertexBuffer, vertex_index);
     glDrawArrays(GL_LINE_STRIP, 0, length);
 }
diff --git a/src/renderer/line_bucket.cpp b/src/renderer/line_bucket.cpp
index 5cad0ddd4e..213d8a2856 100644
--- a/src/renderer/line_bucket.cpp
+++ b/src/renderer/line_bucket.cpp
@@ -21,7 +21,7 @@ using namespace llmr;
 LineBucket::LineBucket(const std::shared_ptr<LineBuffer>& buffer, const BucketDescription& bucket_desc)
     : geometry(bucket_desc.geometry),
       buffer(buffer),
-      start(buffer->length()),
+      start(buffer->index()),
       length(0) {
 }
 
@@ -258,7 +258,7 @@ void LineBucket::addGeometry(const std::vector<Coordinate>& vertices) {
     }
 
     // Update the length.
-    length = buffer->length() - start;
+    length = buffer->index() - start;
 }
 
 void LineBucket::render(Painter& painter, const std::string& layer_name, const Tile::ID& id) {
diff --git a/src/renderer/painter.cpp b/src/renderer/painter.cpp
index 31f8a83331..a00ead94fd 100644
--- a/src/renderer/painter.cpp
+++ b/src/renderer/painter.cpp
@@ -96,7 +96,7 @@ void Painter::drawClippingMask() {
 
     // Draw the clipping mask
     glUniform4f(plainShader->u_color, 1.0f, 0.0f, 1.0f, 1.0f);
-    glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.length());
+    glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.index());
 
     // glEnable(GL_STENCIL_TEST);
     glStencilFunc(GL_EQUAL, 0x80, 0x80);
@@ -265,7 +265,7 @@ void Painter::renderFill(FillBucket& bucket, const std::string& layer_name, cons
 
         // Draw a rectangle that covers the entire viewport.
         coveringPatternArray.bind(*patternShader, tileStencilBuffer, BUFFER_OFFSET(0));
-        glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.length());
+        glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.index());
 
     } else {
         // Draw filling rectangle.
@@ -275,7 +275,7 @@ void Painter::renderFill(FillBucket& bucket, const std::string& layer_name, cons
 
         // Draw a rectangle that covers the entire viewport.
         coveringPlainArray.bind(*plainShader, tileStencilBuffer, BUFFER_OFFSET(0));
-        glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.length());
+        glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.index());
     }
 
     glStencilMask(0x00);
@@ -365,16 +365,16 @@ void Painter::renderDebug(const Tile::Ptr& tile) {
     tileBorderArray.bind(*plainShader, tileBorderBuffer, BUFFER_OFFSET(0));
     glUniform4f(plainShader->u_color, 1.0f, 0.0f, 0.0f, 1.0f);
     glLineWidth(4.0f);
-    glDrawArrays(GL_LINE_STRIP, 0, tileBorderBuffer.length());
+    glDrawArrays(GL_LINE_STRIP, 0, tileBorderBuffer.index());
 
     // draw debug info
     tile->debugFontArray.bind(*plainShader, tile->debugFontBuffer, BUFFER_OFFSET(0));
     glUniform4f(plainShader->u_color, 1.0f, 1.0f, 1.0f, 1.0f);
     glLineWidth(4.0f);
-    glDrawArrays(GL_LINES, 0, tile->debugFontBuffer.length());
+    glDrawArrays(GL_LINES, 0, tile->debugFontBuffer.index());
     glUniform4f(plainShader->u_color, 0.0f, 0.0f, 0.0f, 1.0f);
     glLineWidth(2.0f);
-    glDrawArrays(GL_LINES, 0, tile->debugFontBuffer.length());
+    glDrawArrays(GL_LINES, 0, tile->debugFontBuffer.index());
 
     // Revert blending mode to blend to the back.
     glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_ONE);
@@ -391,7 +391,7 @@ void Painter::renderMatte() {
     // Draw the clipping mask
     matteArray.bind(*plainShader, matteBuffer, BUFFER_OFFSET(0));
     glUniform4fv(plainShader->u_color, 1, white.data());
-    glDrawArrays(GL_TRIANGLES, 0, matteBuffer.length());
+    glDrawArrays(GL_TRIANGLES, 0, matteBuffer.index());
 
     glEnable(GL_STENCIL_TEST);
 }
@@ -405,5 +405,5 @@ void Painter::renderBackground() {
     // Draw the clipping mask
     coveringPlainArray.bind(*plainShader, tileStencilBuffer, BUFFER_OFFSET(0));
     glUniform4fv(plainShader->u_color, 1, white.data());
-    glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.length());
+    glDrawArrays(GL_TRIANGLES, 0, tileStencilBuffer.index());
 }