From 2541f26dda7544732b31166c7a625ff3bb0ad3c9 Mon Sep 17 00:00:00 2001
From: ti_mo <timo.niemann@campus.tu-berlin.de>
Date: Fri, 29 May 2026 16:37:06 +0200
Subject: [PATCH] buggy, but better, mouse zoom works most of the time, a
 strange bug occures when x and y are near zero, sdl then takes no mouse
 events anymore

---
 SimpleImageViewer.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/SimpleImageViewer.c b/SimpleImageViewer.c
index f323f96..1cc9762 100644
--- a/SimpleImageViewer.c
+++ b/SimpleImageViewer.c
@@ -95,12 +95,25 @@ int clamp_low(const int in, const int low){
     return in < low ? low : in;
 }
 
-void on_wheel(SDL_Event* event, SDL_Window* window){
-    printf("a");
+void on_wheel(SDL_Event* event, SDL_Window* window) {
     int last_w, last_h;
     SDL_GetWindowSize(window, &last_w, &last_h);
-    int new_w = clamp_low(last_w + (int)event->wheel.y, 50);
-    SDL_SetWindowSize(window, new_w, new_w * last_h / last_w);
+
+    int step = event->wheel.y * 25;
+    int new_w = clamp_low(last_w + step, 50);
+    int new_h = new_w * last_h / last_w;
+
+    int dx = new_w - last_w;
+    int dy = new_h - last_h;
+
+    int x, y;
+    SDL_GetWindowPosition(window, &x, &y);
+
+    x -= dx / 2;
+    y -= dy / 2;
+
+    SDL_SetWindowPosition(window, x, y);
+    SDL_SetWindowSize(window, new_w, new_h);
 }
 
 int main(int argc, char** argv){
@@ -122,8 +135,6 @@ int main(int argc, char** argv){
         exit(3);
     }
 
-    printf("Dimensions: Width = %d, Height = %d\n", image.x, image.y);
-
     SDL_Window* window = create_window("SimpleImageViewer", image.x, image.y);
     if(!window){
         printf("Failed to create window!");
@@ -160,14 +171,14 @@ int main(int argc, char** argv){
             if(event.type == SDL_EVENT_QUIT || event.type == SDL_EVENT_WINDOW_CLOSE_REQUESTED) run = false;
             if(event.type == SDL_EVENT_MOUSE_BUTTON_DOWN && event.button.button == SDL_BUTTON_LEFT){
                 drag_mouse = true;
-                last_pointer_x = (int)event.motion.x;
-                last_pointer_y = (int)event.motion.y;
+                last_pointer_x = (int)event.button.x;
+                last_pointer_y = (int)event.button.y;
             }
             if(event.type == SDL_EVENT_MOUSE_BUTTON_UP && event.button.button == SDL_BUTTON_LEFT) drag_mouse = false;
             if(event.type == SDL_EVENT_MOUSE_MOTION && drag_mouse){
                 int last_x, last_y;
                 SDL_GetWindowPosition(window, &last_x, &last_y);
-                SDL_SetWindowPosition(window, last_x + (int)event.motion.x - last_pointer_x, last_y + (int)event.motion.y - last_pointer_y);
+                SDL_SetWindowPosition(window, last_x + (int)event.button.x - last_pointer_x, last_y + (int)event.button.y - last_pointer_y);
             }
             if(event.type == SDL_EVENT_MOUSE_WHEEL){
                 on_wheel(&event, window);