feat(render): style, GLSL line/text pipelines, staging batches, bitmap font

src/render/buffer.cpp

@@ -0,0 +1,32 @@
+#include <plot/render/buffer.hpp>
+
+namespace plot::render {
+namespace detail {
+
+bool InstanceStore::create(Status* st) noexcept {
+  // plot::gl::Buffer::create() already reports Unsupported while the entry
+  // points are unresolved and GLFailure when the driver hands out no name, so
+  // the wrapper only has to propagate its answer.
+  if (!buffer_.create(st)) {
+    return false;
+  }
+  capacity_ = 0;
+  return true;
+}
+
+void InstanceStore::upload(const void* data, u32 count, usize instance_bytes) noexcept {
+  if (buffer_.id() == 0 || count == 0 || instance_bytes == 0) {
+    return;
+  }
+  if (count > capacity_) {
+    // Only a workload larger than anything staged so far pays for an
+    // allocation; a frame that repeats the previous one writes into the store
+    // that is already there.
+    buffer_.upload(nullptr, static_cast<usize>(count) * instance_bytes, gl::GL_STREAM_DRAW);
+    capacity_ = count;
+  }
+  buffer_.upload_sub(data, static_cast<usize>(count) * instance_bytes, 0);
+}
+
+}  // namespace detail
+}  // namespace plot::render