Implement very dramatic scrolling that makes you barf

main.c

@@ -11,6 +11,11 @@
 
 #include "./editor.h"
 
+#define SCREEN_WIDTH 800
+#define SCREEN_HEIGHT 600
+#define FPS 60
+#define DELTA_TIME (1.0f / FPS)
+
 #define FONT_WIDTH 128
 #define FONT_HEIGHT 64
 #define FONT_COLS 18
@@ -139,6 +144,8 @@ void render_text_sized(SDL_Renderer *renderer, Font *font, const char *text, siz
 }
 
 Editor editor = {0};
+Vec2f camera_pos = {0};
+Vec2f camera_vel = {0};
 
 #define UNHEX(color) \
     ((color) >> (8 * 0)) & 0xFF, \
@@ -146,11 +153,28 @@ Editor editor = {0};
     ((color) >> (8 * 2)) & 0xFF, \
     ((color) >> (8 * 3)) & 0xFF
 
-void render_cursor(SDL_Renderer *renderer, const Font *font)
+Vec2f window_size(SDL_Window *window)
+{
+    int w, h;
+    SDL_GetWindowSize(window, &w, &h);
+    return vec2f((float) w, (float) h);
+}
+
+Vec2f camera_project_point(SDL_Window *window, Vec2f point)
+{
+    return vec2f_add(
+               vec2f_sub(point, camera_pos),
+               vec2f_mul(window_size(window), vec2fs(0.5f)));
+}
+
+
+void render_cursor(SDL_Renderer *renderer, SDL_Window *window, const Font *font)
 {
     const Vec2f pos =
-        vec2f((float) editor.cursor_col * FONT_CHAR_WIDTH * FONT_SCALE,
-              (float) editor.cursor_row * FONT_CHAR_HEIGHT * FONT_SCALE);
+        camera_project_point(
+            window,
+            vec2f((float) editor.cursor_col * FONT_CHAR_WIDTH * FONT_SCALE,
+                  (float) editor.cursor_row * FONT_CHAR_HEIGHT * FONT_SCALE));
 
     const SDL_Rect rect = {
         .x = (int) floorf(pos.x),
@@ -176,7 +200,6 @@ void usage(FILE *stream)
 
 // TODO: Save file
 // TODO: ncurses renderer
-// TODO: scrolling
 // TODO: Jump forward/backward by a word
 // TODO: Delete a word
 // TODO: Blinking cursor
@@ -202,7 +225,9 @@ int main(int argc, char **argv)
     scc(SDL_Init(SDL_INIT_VIDEO));
 
     SDL_Window *window =
-        scp(SDL_CreateWindow("Text Editor", 0, 0, 800, 600,
+        scp(SDL_CreateWindow("Text Editor",
+                             0, 0,
+                             SCREEN_WIDTH, SCREEN_HEIGHT,
                              SDL_WINDOW_RESIZABLE));
 
     SDL_Renderer *renderer =
@@ -213,6 +238,7 @@ int main(int argc, char **argv)
 
     bool quit = false;
     while (!quit) {
+        const Uint32 start = SDL_GetTicks();
         SDL_Event event = {0};
         while (SDL_PollEvent(&event)) {
             switch (event.type) {
@@ -279,16 +305,36 @@ int main(int argc, char **argv)
             }
         }
 
+        {
+            const Vec2f cursor_pos =
+                vec2f((float) editor.cursor_col * FONT_CHAR_WIDTH * FONT_SCALE,
+                      (float) editor.cursor_row * FONT_CHAR_HEIGHT * FONT_SCALE);
+
+            camera_vel = vec2f_mul(
+                             vec2f_sub(cursor_pos, camera_pos),
+                             vec2fs(2.0f));
+
+            camera_pos = vec2f_add(camera_pos, vec2f_mul(camera_vel, vec2fs(DELTA_TIME)));
+        }
+
+
         scc(SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0));
         scc(SDL_RenderClear(renderer));
 
         for (size_t row = 0; row < editor.size; ++row) {
             const Line *line = editor.lines + row;
-            render_text_sized(renderer, &font, line->chars, line->size, vec2f(0.0f, (float) row * FONT_CHAR_HEIGHT * FONT_SCALE), 0xFFFFFFFF, FONT_SCALE);
+            const Vec2f line_pos = camera_project_point(window, vec2f(0.0f, (float) row * FONT_CHAR_HEIGHT * FONT_SCALE));
+            render_text_sized(renderer, &font, line->chars, line->size, line_pos, 0xFFFFFFFF, FONT_SCALE);
         }
-        render_cursor(renderer, &font);
+        render_cursor(renderer, window, &font);
 
         SDL_RenderPresent(renderer);
+
+        const Uint32 duration = SDL_GetTicks() - start;
+        const Uint32 delta_time_ms = 1000 / FPS;
+        if (duration < delta_time_ms) {
+            SDL_Delay(delta_time_ms - duration);
+        }
     }
 
     SDL_Quit();