From 54d323b5b66d766b636561317d4e139c79ad3fc9 Mon Sep 17 00:00:00 2001
From: Harry Jeffery <harry@exec64.co.uk>
Date: Thu, 5 Nov 2015 23:12:55 +0000
Subject: Add click-drag and mousewheel navigation.

---
 main.c | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/main.c b/main.c
index 2988e12..9174765 100644
--- a/main.c
+++ b/main.c
@@ -3,6 +3,14 @@
 
 SDL_Texture* imv_load_image(SDL_Renderer *r, const char* path);
 
+double clamp(double v, double min, double max) {
+  if(v < min)
+    return min;
+  if(v > max)
+    return max;
+  return v;
+}
+
 int main(int argc, char** argv)
 {
   if(argc < 2) {
@@ -34,7 +42,10 @@ int main(int argc, char** argv)
   int next_path = 0;
   SDL_Texture *img = NULL;
 
-  double scale = 1;
+  struct {
+    double scale;
+    int x, y;
+  } view = {1,0,0};
   int quit = 0;
   int redraw = 1;
   while(!quit) {
@@ -59,15 +70,26 @@ int main(int argc, char** argv)
                 next_path = num_paths - 1;
               break;
             case SDLK_UP:
-              scale = (scale + 0.1 < 10) ? scale + 0.1 : scale;
+              view.scale = clamp(view.scale + 0.1, 1, 10);
               redraw = 1;
               break;
             case SDLK_DOWN:
-              scale = (scale - 0.1 >= 1) ? scale - 0.1 : scale;
+              view.scale = clamp(view.scale - 0.1, 1, 10);
               redraw = 1;
               break;
           }
           break;
+        case SDL_MOUSEWHEEL:
+          view.scale = clamp(view.scale + (0.1 * e.wheel.y), 1, 10);
+          redraw = 1;
+          break;
+        case SDL_MOUSEMOTION:
+          if(e.motion.state & SDL_BUTTON_LMASK) {
+            view.x += e.motion.xrel;
+            view.y += e.motion.yrel;
+            redraw = 1;
+          }
+          break;
         case SDL_WINDOWEVENT:
           redraw = 1;
           break;
@@ -86,7 +108,9 @@ int main(int argc, char** argv)
         img = NULL;
       }
       img = imv_load_image(renderer, paths[cur_path]);
-      scale = 1;
+      view.scale = 1;
+      view.x = 0;
+      view.y = 0;
       redraw = 1;
     }
 
@@ -97,8 +121,13 @@ int main(int argc, char** argv)
         int img_w, img_h, img_access;
         unsigned int img_format;
         SDL_QueryTexture(img, &img_format, &img_access, &img_w, &img_h);
-        SDL_Rect area = {0,0,img_w*scale,img_h*scale};
-        SDL_RenderCopy(renderer, img, &area, &area);
+        SDL_Rect view_area = {
+          view.x,
+          view.y,
+          img_w * view.scale,
+          img_h * view.scale
+        };
+        SDL_RenderCopy(renderer, img, NULL, &view_area);
       }
 
       SDL_RenderPresent(renderer);
-- 
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