Render to cache that only updates on click

This is to prevent slowdown when drawing per frame. Previously, the
program would draw each individual triangle each frame. Now the draws
are cached to a texture that is drawn each frame, and the cache is
recreated on click or undo/redo events.

src/state.cpp

@@ -38,6 +38,16 @@ bgColor(sf::Color::Black)
     pointCircle.setOutlineThickness(1.0f);
 
     saveFilenameBuffer.fill(0);
+
+    if(!drawCache.create(800, 600)) {
+#ifndef NDEBUG
+        puts("ERROR: Failed to initialize RenderTexture (draw cache)");
+#endif
+        flags.reset(8);
+    } else {
+        flags.set(8);
+        drawCacheSprite.setTexture(drawCache.getTexture(), true);
+    }
 }
 
 Tri::State::~State() {
@@ -56,6 +66,7 @@ void Tri::State::handle_events() {
                 if(event.key.code == sf::Keyboard::H) {
                     flags.flip(0);
                 } else if(event.key.code == sf::Keyboard::U) {
+                    flags.set(7);
                     if(currentTri_state > 0) {
                         switch(currentTri_state) {
                         case FIRST:
@@ -72,6 +83,7 @@ void Tri::State::handle_events() {
                         --trisIndex;
                     }
                 } else if(event.key.code == sf::Keyboard::R) {
+                    flags.set(7);
                     if(currentTri_state != CurrentState::NONE
                             && currentTri_state < currentTri_maxState) {
                         switch(currentTri_state) {
@@ -109,7 +121,8 @@ void Tri::State::handle_events() {
                 }
             }
         } else if(event.type == sf::Event::MouseButtonPressed) {
-            if(!flags.test(2) && !flags.test(5) && !flags.test(6)) {
+            if(!is_in_clickable_menu()) {
+                flags.set(7);
                 switch(currentTri_state) {
                 case CurrentState::NONE:
                     currentTri[0] = sf::Vector2f(event.mouseButton.x, event.mouseButton.y);
@@ -184,7 +197,18 @@ void Tri::State::update() {
 }
 
 void Tri::State::draw() {
-    draw_to_target(&window);
+    if(flags.test(8)) {
+        // draw cache initialized
+        if(flags.test(7)) {
+            // draw cache dirty
+            flags.reset(7);
+            draw_to_target(&drawCache);
+            drawCache.display();
+        }
+        window.draw(drawCacheSprite);
+    } else {
+        draw_to_target(&window);
+    }
 
     // draw gui stuff
     ImGui::SFML::Render(window);
@@ -276,3 +300,7 @@ std::string_view Tri::State::failed_save_message() const {
 void Tri::State::close_save() {
     flags.reset(6);
 }
+
+bool Tri::State::is_in_clickable_menu() const {
+    return flags.test(2) || flags.test(5) || flags.test(6);
+}

src/state.hpp

@@ -24,6 +24,8 @@ namespace Tri {
          * 4 - bg color picker color dirty
          * 5 - display bg color picker
          * 6 - draw save
+         * 7 - draw cache dirty
+         * 8 - draw cache initialized
          */
         typedef std::bitset<64> BitsetType;
         BitsetType flags;
@@ -50,6 +52,9 @@ namespace Tri {
         FilenameBufferType saveFilenameBuffer;
         std::string failedSaveMessage;
 
+        sf::RenderTexture drawCache;
+        sf::Sprite drawCacheSprite;
+
     public:
         void handle_events();
         void update();
@@ -73,6 +78,9 @@ namespace Tri {
         bool do_save();
         std::string_view failed_save_message() const;
         void close_save();
+
+    private:
+        bool is_in_clickable_menu() const;
     };
 }