add screenshot capturing

Author: marginalhours

README.md

@@ -41,7 +41,8 @@ Click + drag to draw a rectangle to zoom into.
 
 ### Keyboard
 
-- <kbd>space</kbd> -- reset viewer
+- <kbd>space</kbd> -- take screenshot
+- <kbd>r</kbd> -- reset viewer
 - <kbd>+</kbd>/<kbd>=</kbd> -- zoom in
 - <kbd>-</kbd> -- zoom out
 - <kbd>.</kbd> -- increase detail (iterations)

src/input.cpp

@@ -2,7 +2,7 @@
 #include "SDL.h"
 #include <iostream>
 
-void Input::HandleInput(Mandelbrot &instance) const {
+void Input::handleInput(Mandelbrot &instance, Renderer &renderer) const {
   SDL_Event e;
 
   while (SDL_PollEvent(&e)) {
@@ -65,6 +65,10 @@ void Input::HandleInput(Mandelbrot &instance) const {
         break;
       }
       case SDLK_SPACE: {
+        renderer.captureScreenshot();
+        break;
+      }
+      case SDLK_r: {
         instance.resetBounds();
         break;
       }

src/input.h

@@ -5,10 +5,11 @@
 
 // forward declaration for use in function signature
 class Mandelbrot;
+class Renderer;
 
 class Input {
 public:
-  void HandleInput(Mandelbrot &instance) const;
+  void handleInput(Mandelbrot &instance, Renderer &renderer) const;
 };
 
 #endif

src/mandelbrot.cpp

@@ -63,7 +63,6 @@ void renderLoop(MessageQueue<RenderOptions> &queue, bool &running) {
     if (options) {
       updatePixelsInRange(options.value());
     }
-    std::cout << running << std::endl;
   }
 }
 
@@ -78,6 +77,7 @@ void Mandelbrot::resetBounds() {
   zoom = 1.0;
   center_y = 0.0;
   center_x = -1.0;
+  max_iterations = 50;
   setBoundsFromState();
 }
 
@@ -206,7 +206,7 @@ void Mandelbrot::run(Input const &Input, Renderer &renderer) {
   Uint32 prev_frame_end = SDL_GetTicks();
 
   while (running) {
-    Input.HandleInput(*this);
+    Input.handleInput(*this, renderer);
 
     Uint32 frame_start = SDL_GetTicks();
 
@@ -217,7 +217,7 @@ void Mandelbrot::run(Input const &Input, Renderer &renderer) {
 
       Uint32 calculate_duration = SDL_GetTicks() - frame_start;
 
-      renderer.updateWindowTitle(calculate_duration);
+      renderer.updateWindowTitle(max_iterations, x_min, x_max, y_min, y_max);
       dirty = false;
     }
 

src/renderer.cpp

@@ -1,4 +1,5 @@
 #include "renderer.h"
+#include <filesystem>
 #include <iostream>
 #include <string>
 
@@ -51,6 +52,31 @@ Renderer::~Renderer() {
   SDL_Quit();
 }
 
+void Renderer::captureScreenshot() {
+  SDL_Surface *screenshot =
+      SDL_CreateRGBSurface(0, screen_width, screen_height, 32, 0x00ff0000,
+                           0x0000ff00, 0x000000ff, 0xff000000);
+
+  SDL_RenderReadPixels(sdl_renderer, NULL, SDL_PIXELFORMAT_ARGB8888,
+                       screenshot->pixels, screenshot->pitch);
+
+  // Figure out the next free screenshot path will be
+  unsigned int next_screenshot_slot = 0;
+  std::filesystem::path output_path{
+      "screenshot-" + std::to_string(next_screenshot_slot) + ".bmp"};
+
+  while (std::filesystem::exists(output_path)) {
+    next_screenshot_slot++;
+    output_path = std::filesystem::path(
+        "screenshot-" + std::to_string(next_screenshot_slot) + ".bmp");
+  }
+
+  SDL_SaveBMP(screenshot, output_path.c_str());
+  SDL_FreeSurface(screenshot);
+
+  std::cout << "Wrote out " << output_path << std::endl;
+}
+
 void Renderer::render(SDL_Rect selection) {
 
   // Apply pixels vector to texture
@@ -74,7 +100,16 @@ void Renderer::render(SDL_Rect selection) {
   SDL_RenderPresent(sdl_renderer);
 }
 
-void Renderer::updateWindowTitle(unsigned int render_time) {
-  std::string title{"Mandelbrot -- last render " + std::to_string(render_time)};
+void Renderer::updateWindowTitle(unsigned int iterations, double x_min,
+                                 double x_max, double y_min, double y_max) {
+  std::string title{std::to_string(iterations) + " iterations -- top left (" +
+                    std::to_string(x_min) + "," + std::to_string(y_min) +
+                    ") bottom right (" + std::to_string(x_max) + "," +
+                    std::to_string(y_max) + ")"};
+
+  // Change window title to reflect current view
   SDL_SetWindowTitle(sdl_window, title.c_str());
+
+  // Log title also to console for debugging purposes
+  std::cout << title << std::endl;
 }

src/renderer.h

@@ -10,8 +10,11 @@ class Renderer {
   Renderer(unsigned int screen_width, unsigned int screen_height);
   ~Renderer();
 
+  void captureScreenshot();
+
   void render(SDL_Rect selection);
-  void updateWindowTitle(unsigned int render_time);
+  void updateWindowTitle(unsigned int iterations, double x_min, double x_max,
+                         double y_min, double y_max);
 
   // get mutable access to pixel data
   std::vector<Uint32> &getPixels() { return pixels; };