draw_sampling.h

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#ifndef YAZE_APP_GUI_CORE_DRAW_SAMPLING_H_
#define YAZE_APP_GUI_CORE_DRAW_SAMPLING_H_
 
#include "imgui/imgui.h"
 
namespace yaze {
namespace gui {
 
class ScopedNearestSampling {
 public:
  explicit ScopedNearestSampling(ImDrawList* draw_list) {
    if (draw_list == nullptr || IsActiveOn(draw_list)) {
      return;
    }
    ImDrawCallback set_nearest =
        ImGui::GetPlatformIO().DrawCallback_SetSamplerNearest;
    if (set_nearest == nullptr) {
      return;
    }
    draw_list->AddCallback(set_nearest, nullptr);
    draw_list_ = draw_list;
    outer_ = innermost_;
    innermost_ = this;
  }
 
  ~ScopedNearestSampling() {
    if (draw_list_ == nullptr) {
      return;
    }
    innermost_ = outer_;
    const ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
    if (platform_io.DrawCallback_SetSamplerLinear != nullptr) {
      draw_list_->AddCallback(platform_io.DrawCallback_SetSamplerLinear,
                              nullptr);
    } else if (platform_io.DrawCallback_ResetRenderState != nullptr) {
      draw_list_->AddCallback(platform_io.DrawCallback_ResetRenderState,
                              nullptr);
    }
  }
 
  ScopedNearestSampling(const ScopedNearestSampling&) = delete;
  ScopedNearestSampling& operator=(const ScopedNearestSampling&) = delete;
 
  // True when this scope added the nearest callback and will restore it.
  bool active() const { return draw_list_ != nullptr; }
 
 private:
  static bool IsActiveOn(const ImDrawList* draw_list) {
    for (const ScopedNearestSampling* scope = innermost_; scope != nullptr;
         scope = scope->outer_) {
      if (scope->draw_list_ == draw_list) {
        return true;
      }
    }
    return false;
  }
 
  ImDrawList* draw_list_ = nullptr;
  const ScopedNearestSampling* outer_ = nullptr;
 
  // Innermost active scope on this thread; scopes link to the one they nest
  // in through outer_.
  static inline thread_local const ScopedNearestSampling* innermost_ = nullptr;
};
 
}  // namespace gui
}  // namespace yaze
 
#endif  // YAZE_APP_GUI_CORE_DRAW_SAMPLING_H_