Various small improvements

- fix some warnings about struct/class deslaration/definition mismatch
- fix incorrect assert in jpegcontent.cpp
- add a note
- null a pointer after deleting a job

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>
(cherry picked from commit d4548234b9)

src/gvcore/filethumbnailview.cpp

@@ -388,6 +388,7 @@ void FileThumbnailView::doStartThumbnailUpdate(const KFileItemList* list) {
 void FileThumbnailView::stopThumbnailUpdate() {
 	if (!d->mThumbnailLoadJob.isNull()) {
 		d->mThumbnailLoadJob->kill(false);
+		d->mThumbnailLoadJob=NULL;
 	}
 }
 

src/gvcore/filethumbnailview.h

@@ -105,7 +105,7 @@ protected:
 	virtual void keyPressEvent( TQKeyEvent* );
 
 private:
-	class Private;
+	struct Private;
 	Private* d;
 
 	void updateGrid();

src/gvcore/filethumbnailviewitem.cpp

@@ -283,8 +283,11 @@ void FileThumbnailViewItem::calcRect(const TQString&) {
 		itemTextRect.moveLeft(PADDING);
 		itemTextRect.moveTop(thumbnailSize + PADDING * 2);
 	}
-	
+
 	// Update rects
+	// NOTE: this results in 3 calls to TQIconViewContainer(), which is costly if
+	//       there are a lot (tens of thousands) of items, unfortunately there
+	//       is no way to workaround this in current (14.1.1, 2024) TQt API
 	if ( itemPixmapRect != pixmapRect() ) {
 		setPixmapRect( itemPixmapRect );
 	}

src/gvcore/fileviewcontroller.cpp

@@ -172,8 +172,7 @@ private:
 // FileViewController::Private
 //
 //-----------------------------------------------------------------------
-class FileViewController::Private {
-public:
+struct FileViewController::Private {
 	~Private() {
 		delete mSliderTracker;
 	}

src/imageutils/jpegcontent.cpp

@@ -88,7 +88,7 @@ int inmem_fill_input_buffer(j_decompress_ptr cinfo) {
 
 void inmem_skip_input_data(j_decompress_ptr cinfo, long num_bytes) {
 	if (num_bytes<=0) return;
-	Q_ASSERT(num_bytes>=long(cinfo->src->bytes_in_buffer));
+	Q_ASSERT(num_bytes<=long(cinfo->src->bytes_in_buffer));
 	cinfo->src->next_input_byte+=num_bytes;
 	cinfo->src->bytes_in_buffer-=num_bytes;
 }