From c690747bd2032cbee0f2ee1c94470847cbd95e2b Mon Sep 17 00:00:00 2001
From: David Capello <david@igarastudio.com>
Date: Wed, 3 Apr 2019 21:19:44 -0300
Subject: [PATCH] Improve color conversion preview without clearing the old
 image

It is better for continuous preview feedback to keep the old image so
the new preview result is painted above the old one (and there is no
flicker effects).
---
 src/app/commands/cmd_change_pixel_format.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/app/commands/cmd_change_pixel_format.cpp b/src/app/commands/cmd_change_pixel_format.cpp
index 8fe26fd37..309971218 100644
--- a/src/app/commands/cmd_change_pixel_format.cpp
+++ b/src/app/commands/cmd_change_pixel_format.cpp
@@ -174,6 +174,7 @@ public:
     , m_imageBuffer(new doc::ImageBuffer)
     , m_selectedItem(nullptr)
     , m_ditheringSelector(nullptr)
+    , m_imageJustCreated(true)
   {
     doc::PixelFormat from = m_editor->sprite()->pixelFormat();
 
@@ -311,6 +312,10 @@ private:
                     visibleBounds.w,
                     visibleBounds.h,
                     m_imageBuffer));
+    if (m_imageJustCreated) {
+      m_imageJustCreated = false;
+      m_image->clear(0);
+    }
 
     m_editor->renderEngine().setPreviewImage(
       nullptr,
@@ -319,7 +324,6 @@ private:
       visibleBounds.origin(),
       doc::BlendMode::SRC);
 
-    m_image->clear(0);
     m_editor->invalidate();
     progress()->setValue(0);
     progress()->setVisible(true);
@@ -370,6 +374,7 @@ private:
   std::unique_ptr<ConvertThread> m_bgThread;
   ConversionItem* m_selectedItem;
   DitheringSelector* m_ditheringSelector;
+  bool m_imageJustCreated;
 };
 
 } // anonymous namespace