add file picking for osx and ios and implement equirectangular import

PanoPainter-OSX/main.cpp

@@ -26,6 +26,29 @@
 {
     CGLFlushDrawable([glctx CGLContextObj]);
 }
+- (std::string)pick_file
+{
+    NSOpenPanel *panel = [NSOpenPanel openPanel];
+    [panel setCanChooseFiles:YES];
+    [panel setCanChooseDirectories:NO];
+    [panel setAllowsMultipleSelection:NO]; // yes if more than one dir is allowed
+    
+    NSArray* fileTypes = [NSArray arrayWithObjects:@"png", @"PNG", @"jpg", @"JPG", @"jpeg", nil];
+    [panel setAllowedFileTypes:fileTypes];
+
+    NSInteger clicked = [panel runModal];
+
+    std::string ret;
+    if (clicked == NSFileHandlingPanelOKButton)
+    {
+        for (NSURL *url in [panel URLs])
+        {
+            LOG("selected file: %s", [[url path] cStringUsingEncoding:NSUTF8StringEncoding]);
+            ret = [[url path] cStringUsingEncoding:NSUTF8StringEncoding];
+        }
+    }
+    return ret;
+}
 - (instancetype)initWithFrame:(NSRect)frameRect
 {
     gl_ready = false;

PanoPainter-OSX/main.h

@@ -14,4 +14,5 @@
 - (void)async_lock;
 - (void)async_unlock;
 - (void)async_swap;
+- (std::string)pick_file;
 @end