Implement a workaround for a bug in WPF that causes a freeze

src/.editorconfig

@@ -79,9 +79,9 @@ dotnet_style_allow_statement_immediately_after_block_experimental = true:silent
 ###############################
 [*.cs]
 # var preferences
-csharp_style_var_for_built_in_types = false:suggestion
-csharp_style_var_when_type_is_apparent = false:silent
-csharp_style_var_elsewhere = false:suggestion
+# csharp_style_var_for_built_in_types = false:suggestion
+# csharp_style_var_when_type_is_apparent = false:silent
+# csharp_style_var_elsewhere = false:suggestion
 # Expression-bodied members
 csharp_style_expression_bodied_methods = false:silent
 csharp_style_expression_bodied_constructors = false:silent

src/.editorconfig.bak

@@ -0,0 +1,158 @@
+# To learn more about .editorconfig see https://aka.ms/editorconfigdocs
+###############################
+# Core EditorConfig Options   #
+###############################
+# All files
+[*]
+indent_style = space
+
+# XML project files
+[*.{csproj,vbproj,vcxproj,vcxproj.filters,proj,projitems,shproj}]
+indent_size = 2
+
+# XML config files
+[*.{props,targets,ruleset,config,nuspec,resx,vsixmanifest,vsct}]
+indent_size = 2
+
+# Code files
+[*.{cs,csx,vb,vbx}]
+indent_size = 4
+insert_final_newline = true
+charset = utf-8-bom
+###############################
+# .NET Coding Conventions     #
+###############################
+[*.{cs,vb}]
+# Organize usings
+dotnet_sort_system_directives_first = true
+# this. preferences
+dotnet_style_qualification_for_field = false:silent
+dotnet_style_qualification_for_property = false:silent
+dotnet_style_qualification_for_method = false:silent
+dotnet_style_qualification_for_event = false:silent
+# Language keywords vs BCL types preferences
+dotnet_style_predefined_type_for_locals_parameters_members = true:silent
+dotnet_style_predefined_type_for_member_access = true:silent
+# Parentheses preferences
+dotnet_style_parentheses_in_arithmetic_binary_operators = always_for_clarity:silent
+dotnet_style_parentheses_in_relational_binary_operators = always_for_clarity:silent
+dotnet_style_parentheses_in_other_binary_operators = always_for_clarity:silent
+dotnet_style_parentheses_in_other_operators = never_if_unnecessary:silent
+# Modifier preferences
+dotnet_style_require_accessibility_modifiers = for_non_interface_members:silent
+dotnet_style_readonly_field = true:suggestion
+# Expression-level preferences
+dotnet_style_object_initializer = true:suggestion
+dotnet_style_collection_initializer = true:suggestion
+dotnet_style_explicit_tuple_names = true:suggestion
+dotnet_style_null_propagation = true:suggestion
+dotnet_style_coalesce_expression = true:suggestion
+dotnet_style_prefer_is_null_check_over_reference_equality_method = true:suggestion
+dotnet_style_prefer_inferred_tuple_names = true:suggestion
+dotnet_style_prefer_inferred_anonymous_type_member_names = true:suggestion
+dotnet_style_prefer_auto_properties = true:silent
+dotnet_style_prefer_conditional_expression_over_assignment = true:silent
+dotnet_style_prefer_conditional_expression_over_return = true:silent
+###############################
+# Naming Conventions          #
+###############################
+# Style Definitions
+dotnet_naming_style.pascal_case_style.capitalization             = pascal_case
+# Use PascalCase for constant fields  
+dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols  = constant_fields
+dotnet_naming_rule.constant_fields_should_be_pascal_case.style = pascal_case_style
+dotnet_naming_symbols.constant_fields.applicable_kinds            = field
+dotnet_naming_symbols.constant_fields.applicable_accessibilities  = *
+dotnet_naming_symbols.constant_fields.required_modifiers          = const
+dotnet_style_operator_placement_when_wrapping = beginning_of_line
+tab_width = 4
+end_of_line = crlf
+dotnet_style_prefer_simplified_boolean_expressions = true:suggestion
+dotnet_style_prefer_compound_assignment = true:suggestion
+dotnet_style_prefer_simplified_interpolation = true:suggestion
+dotnet_style_namespace_match_folder = true:suggestion
+dotnet_style_allow_multiple_blank_lines_experimental = true:silent
+dotnet_style_allow_statement_immediately_after_block_experimental = true:silent
+###############################
+# C# Coding Conventions       #
+###############################
+[*.cs]
+# var preferences
+csharp_style_var_for_built_in_types = false:suggestion
+csharp_style_var_when_type_is_apparent = false:silent
+csharp_style_var_elsewhere = false:suggestion
+# Expression-bodied members
+csharp_style_expression_bodied_methods = false:silent
+csharp_style_expression_bodied_constructors = false:silent
+csharp_style_expression_bodied_operators = false:silent
+csharp_style_expression_bodied_properties = true:silent
+csharp_style_expression_bodied_indexers = true:silent
+csharp_style_expression_bodied_accessors = true:silent
+# Pattern matching preferences
+csharp_style_pattern_matching_over_is_with_cast_check = true:suggestion
+csharp_style_pattern_matching_over_as_with_null_check = true:suggestion
+# Null-checking preferences
+csharp_style_throw_expression = true:suggestion
+csharp_style_conditional_delegate_call = true:suggestion
+# Modifier preferences
+csharp_preferred_modifier_order = public,private,protected,internal,static,extern,new,virtual,abstract,sealed,override,readonly,unsafe,volatile,async:suggestion
+# Expression-level preferences
+csharp_prefer_braces = true:silent
+csharp_style_deconstructed_variable_declaration = true:suggestion
+csharp_prefer_simple_default_expression = true:suggestion
+csharp_style_pattern_local_over_anonymous_function = true:suggestion
+csharp_style_inlined_variable_declaration = true:suggestion
+###############################
+# C# Formatting Rules         #
+###############################
+# New line preferences
+csharp_new_line_before_open_brace = all
+csharp_new_line_before_else = true
+csharp_new_line_before_catch = true
+csharp_new_line_before_finally = true
+csharp_new_line_before_members_in_object_initializers = true
+csharp_new_line_before_members_in_anonymous_types = true
+csharp_new_line_between_query_expression_clauses = true
+# Indentation preferences
+csharp_indent_case_contents = true
+csharp_indent_switch_labels = true
+csharp_indent_labels = flush_left
+# Space preferences
+csharp_space_after_cast = false
+csharp_space_after_keywords_in_control_flow_statements = true
+csharp_space_between_method_call_parameter_list_parentheses = false
+csharp_space_between_method_declaration_parameter_list_parentheses = false
+csharp_space_between_parentheses = false
+csharp_space_before_colon_in_inheritance_clause = true
+csharp_space_after_colon_in_inheritance_clause = true
+csharp_space_around_binary_operators = before_and_after
+csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
+csharp_space_between_method_call_name_and_opening_parenthesis = false
+csharp_space_between_method_call_empty_parameter_list_parentheses = false
+# Wrapping preferences
+csharp_preserve_single_line_statements = true
+csharp_preserve_single_line_blocks = true
+csharp_style_namespace_declarations= file_scoped:silent
+csharp_using_directive_placement = outside_namespace:silent
+csharp_prefer_simple_using_statement = true:suggestion
+csharp_style_expression_bodied_lambdas = true:silent
+csharp_style_expression_bodied_local_functions = false:silent
+csharp_style_prefer_null_check_over_type_check = true:suggestion
+csharp_style_prefer_index_operator = true:suggestion
+csharp_style_prefer_local_over_anonymous_function = true:suggestion
+csharp_style_prefer_range_operator = true:suggestion
+csharp_style_implicit_object_creation_when_type_is_apparent = true:suggestion
+csharp_style_prefer_tuple_swap = true:suggestion
+csharp_style_unused_value_assignment_preference = discard_variable:suggestion
+csharp_style_unused_value_expression_statement_preference = discard_variable:silent
+csharp_prefer_static_local_function = true:suggestion
+csharp_style_allow_embedded_statements_on_same_line_experimental = true:silent
+csharp_style_allow_blank_lines_between_consecutive_braces_experimental = true:silent
+csharp_style_allow_blank_line_after_colon_in_constructor_initializer_experimental = true:silent
+###############################
+# VB Coding Conventions       #
+###############################
+[*.vb]
+# Modifier preferences
+visual_basic_preferred_modifier_order = Partial,Default,Private,Protected,Public,Friend,NotOverridable,Overridable,MustOverride,Overloads,Overrides,MustInherit,NotInheritable,Static,Shared,Shadows,ReadOnly,WriteOnly,Dim,Const,WithEvents,Widening,Narrowing,Custom,Async:suggestion

src/PixiEditor/Models/DocumentModels/ActionAccumulator.cs

@@ -73,19 +73,38 @@ internal class ActionAccumulator
                 helpers.Updater.ApplyChangeFromChangeInfo(info);
             }
 
-            // lock bitmaps that need to be updated
-            var affectedChunks = new AffectedChunkGatherer(helpers.Tracker, changes);
+            // render changes
+            // If you are a sane person or maybe just someone who reads WPF documentation, you might think that the reasonable order of operations should be
+            // 1. Lock the writeable bitmaps
+            // 2. Update their contents
+            // 3. Add dirty rectangles
+            // 4. Unlock them
+            // As it turns out, doing operations in this order leads to WPF render thread crashing in some circumstatances.
+            // Then the whole app freezes without throwing any errors, because the UI thread is blocked on a mutex, waiting for the dead render thread.
+            // This is despite the order clearly being adviced in the documentations here: https://docs.microsoft.com/en-us/dotnet/api/system.windows.media.imaging.writeablebitmap?view=windowsdesktop-6.0&viewFallbackFrom=net-6.0#remarks
+            // Because of that, I'm executing the operations in the order that makes a lot less sense:
+            // 1. Update the contents of the bitmaps
+            // 2. Lock Them
+            // 3. Add dirty rectangles
+            // 4. Unlock
+            // The locks clearly do nothing useful here, and I'm only calling them because WriteableBitmap checks if it's locked before letting you add dirty rectangles.
+            // Really, the locks are supposed to prevent me from updating the bitmap contents in step 1, but they can't since I'm doing direct unsafe memory copying
+            // Somehow this all works
+            // Also, there is a bug report for this on github https://github.com/dotnet/wpf/issues/5816
 
+            var affectedChunks = new AffectedChunkGatherer(helpers.Tracker, changes);
+            bool refreshDelayed = toExecute.Any(static action => action is ChangeBoundary_Action or Redo_Action or Undo_Action);
+            var renderResult = await renderer.UpdateGatheredChunks(affectedChunks, refreshDelayed);
+            
+            // lock bitmaps that need to be updated
             foreach (var (_, bitmap) in document.Bitmaps)
             {
                 bitmap.Lock();
             }
-            bool refreshDelayed = toExecute.Any(static action => action is ChangeBoundary_Action or Redo_Action or Undo_Action);
-            if (refreshDelayed)
-                LockPreviewBitmaps(document.StructureRoot);
 
             // update bitmaps
-            var renderResult = await renderer.UpdateGatheredChunks(affectedChunks, refreshDelayed);
+            if (refreshDelayed)
+                LockPreviewBitmaps(document.StructureRoot);
             AddDirtyRects(renderResult);
 
             // unlock bitmaps