implement basic paint canvas

engine/brush.h

@@ -0,0 +1,58 @@
+#pragma once
+#include "rtt.h"
+
+NS_START
+
+class Brush
+{
+public:
+    int id;
+    std::string m_name;
+    uint16_t m_tex_id;
+    glm::vec4 m_tip_color;
+    float m_tip_size;
+    float m_tip_spacing;
+    float m_tip_flow;
+    float m_tip_angle;
+    float m_jitter_scale;
+    float m_jitter_angle;
+    float m_jitter_spread;
+    float m_jitter_flow;
+};
+
+class Stroke
+{
+public:
+    struct Keypoint
+    {
+        glm::vec2 pos;
+        float pressure;
+    };
+    int m_layer;
+    float m_dist;
+    ui::Brush m_brush;
+    std::vector<Keypoint> m_keypoints;
+    void add_point(glm::vec2 pos, float pressure)
+    {
+        m_keypoints.emplace_back();
+        m_keypoints.back().pos = pos;
+        m_keypoints.back().pressure = pressure;
+    }
+};
+
+class Layer
+{
+public:
+    RTT m_rtt;
+    bool m_visible = true;
+    bool m_locked = false;
+    float m_alpha = 1.f;
+    std::string m_name;
+    bool create(int width, int height, std::string name)
+    {
+        m_rtt.create(width, height);
+        return true;
+    }
+};
+
+NS_END