Don't crash when saving palettes to .jpg format (fix #2654)

Now .jpg is not even show in the list of available format to save
palettes (same for other file format that don't support indexed color
mode).

data/strings/en.ini

@@ -53,6 +53,7 @@ Import Sprite Sheet
 END
 error_loading_file = Error<<Error loading file: {0}||&OK
 error_saving_file = Error<<Error saving file: {0}||&OK
+file_format_doesnt_support_palette = Error<<Cannot save a color palette in {0} format||&OK
 export_animation_in_sequence = <<<END
 Notice
 <<Do you want to export the animation in {0} files?

src/app/commands/cmd_save_palette.cpp

@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -50,7 +51,7 @@ void SavePaletteCommand::onLoadParams(const Params& params)
   m_saveAsPreset = (params.get("saveAsPreset") == "true");
 }
 
-void SavePaletteCommand::onExecute(Context* context)
+void SavePaletteCommand::onExecute(Context* ctx)
 {
   const doc::Palette* palette = get_current_palette();
   std::string filename;
@@ -68,6 +69,18 @@ void SavePaletteCommand::onExecute(Context* context)
       return;
 
     filename = selFilename.front();
+
+    // Check that the file format supports saving indexed images/color
+    // palettes (e.g. if the user specified .jpg we should show that
+    // that file format is not supported to save color palettes)
+    if (!base::has_file_extension(filename, exts)) {
+      if (ctx->isUIAvailable()) {
+        ui::Alert::show(
+          fmt::format(Strings::alerts_file_format_doesnt_support_palette(),
+                      base::get_file_extension(filename)));
+      }
+      return;
+    }
   }
 
   if (!save_palette(filename.c_str(), palette, 16)) // TODO 16 should be configurable
@@ -75,7 +88,7 @@ void SavePaletteCommand::onExecute(Context* context)
 
   if (m_preset == get_default_palette_preset_name()) {
     set_default_palette(palette);
-    if (!context->activeDocument())
+    if (!ctx->activeDocument())
       set_current_palette(palette, false);
   }
   if (m_saveAsPreset) {

src/app/file/file.cpp

@@ -63,11 +63,13 @@ base::paths get_readable_extensions()
   return paths;
 }
 
-base::paths get_writable_extensions()
+base::paths get_writable_extensions(const int requiredFormatFlag)
 {
   base::paths paths;
   for (const FileFormat* format : *FileFormatsManager::instance()) {
-    if (format->support(FILE_SUPPORT_SAVE))
+    if (format->support(FILE_SUPPORT_SAVE) &&
+        (requiredFormatFlag == 0 ||
+         format->support(requiredFormatFlag)))
       format->getExtensions(paths);
   }
   return paths;

src/app/file/file.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2020  Igara Studio S.A.
+// Copyright (C) 2018-2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -281,7 +281,7 @@ namespace app {
 
   // Available extensions for each load/save operation.
   base::paths get_readable_extensions();
-  base::paths get_writable_extensions();
+  base::paths get_writable_extensions(const int requiredFormatFlag = 0);
 
   // High-level routines to load/save documents.
   Doc* load_document(Context* context, const std::string& filename);

src/app/file/jpeg_format.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2020  Igara Studio S.A.
+// Copyright (C) 2018-2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -357,7 +357,9 @@ bool JpegFormat::onSave(FileOp* fop)
   JSAMPARRAY buffer;
   JDIMENSION buffer_height;
   const auto jpeg_options = std::static_pointer_cast<JpegOptions>(fop->formatOptions());
-  const int qualityValue = (int)base::clamp(100.0f * jpeg_options->quality, 0.f, 100.f);
+  const int qualityValue =
+    (jpeg_options ? (int)base::clamp(100.0f * jpeg_options->quality, 0.f, 100.f):
+                    100);
 
   int c;
 

src/app/file/palette_file.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2019  Igara Studio S.A.
+// Copyright (C) 2018-2021  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -47,7 +47,7 @@ base::paths get_readable_palette_extensions()
 
 base::paths get_writable_palette_extensions()
 {
-  base::paths paths = get_writable_extensions();
+  base::paths paths = get_writable_extensions(FILE_SUPPORT_INDEXED);
   for (const char* s : palExts)
     paths.push_back(s);
   return paths;