Allow to set a default filter in file dialogs

native-windows-gui/examples/image_decoder_d.rs

@@ -29,7 +29,7 @@ pub struct ImageDecoderApp {
     #[nwg_resource]
     decoder: nwg::ImageDecoder,
 
-    #[nwg_resource(title: "Open File", action: nwg::FileDialogAction::Open, filters: "Png(*.png)|Jpeg(*.jpg;*.jpeg)|DDS(*.dds)|TIFF(*.tiff)|BMP(*.bmp)|Any (*.*)")]
+    #[nwg_resource(title: "Open File", action: nwg::FileDialogAction::Open, filters: "Png(*.png)|Jpeg(*.jpg;*.jpeg)|DDS(*.dds)|TIFF(*.tiff)|BMP(*.bmp)|>Any (*.*)")]
     dialog: nwg::FileDialog,
 
     #[nwg_control(text: "Open", focus: true)]

native-windows-gui/src/resources/file_dialog.rs

@@ -29,7 +29,8 @@ pub enum FileDialogAction {
     * multiselect: Whether the user can select more than one file. Only supported with the Open action
     * default_folder: Default folder to show in the dialog.
     * filters: If defined, filter the files that the user can select (In a Open dialog) or which extension to add to the saved file (in a Save dialog)
-    The `filters` value must be a '|' separated string having this format: "Test(*.txt;*.rs)|Any(*.*)"  
+    The `filters` value must be a '|' separated string having this format: "Test(*.txt;*.rs)|Any(*.*)".  
+    If one of the filters has its name prefixed with '>' (like ">Test"), it will become the default filter. 
 
     ```rust
         use native_windows_gui as nwg;
@@ -168,7 +169,8 @@ impl FileDialog {
         This can only be set ONCE (the initialization counts) and won't work if the dialog is `OpenDirectory`.  
 
         The `filters` value must be a '|' separated string having this format: "Test(*.txt;*.rs)|Any(*.*)"  
-        Where the fist part is the "human name" and the second part is a filter for the system.
+        Where the first part is the "human name" and the second part is a filter for the system. If the
+        human name starts with a '>', the '>' is removed and the filter associated with it becomes the default.  
     */
     pub fn set_filters<'a>(&self, filters: &'a str) -> Result<(), NwgError> {
         unsafe{ 

native-windows-gui/src/win32/resources_helper.rs

@@ -391,7 +391,7 @@ pub unsafe fn create_file_dialog<'a, 'b>(
     match &filters {
         &Some(ref f) => match file_dialog_set_filters(file_dialog, f) {
             Ok(_) => (),
-            Err(e) => { println!("set filters"); file_dialog.Release(); return Err(e); }
+            Err(e) => { file_dialog.Release(); return Err(e); }
         },
         &None => ()
     }
@@ -456,8 +456,16 @@ pub unsafe fn file_dialog_set_filters<'a>(dialog: &mut IFileDialog, filters: &'a
 
     let mut raw_filters: Vec<COMDLG_FILTERSPEC> = Vec::with_capacity(3);
     let mut keep_alive: Vec<(Vec<u16>, Vec<u16>)> = Vec::with_capacity(3);
+    let mut default_filter = None;
 
     for f in filters.split('|') {
+        let f = if f.starts_with('>') {
+            default_filter = Some(raw_filters.len());
+            f.split_at(1).1
+        } else {
+            f
+        };
+
         let end = f.rfind('(');
         if end.is_none() {
             let err = format!("Bad extension filter format: {:?}", filters);
@@ -473,7 +481,16 @@ pub unsafe fn file_dialog_set_filters<'a>(dialog: &mut IFileDialog, filters: &'a
 
     let filters_count = raw_filters.len() as UINT;
     if dialog.SetFileTypes(filters_count, raw_filters.as_ptr()) == S_OK {
-        Ok(())
+        if let Some(i) = default_filter {
+            if dialog.SetFileTypeIndex((i + 1) as u32) == S_OK {
+                Ok(())
+            } else {
+                let err = format!("Failed to set the default filter using {:?}", filters);
+                return Err(NwgError::file_dialog(&err))
+            }
+        } else {
+            Ok(())
+        }
     } else {
         let err = format!("Failed to set the filters using {:?}", filters);
         return Err(NwgError::file_dialog(&err));