From 9062e0aae9f2f576b7a237c28028aa6b09feee5e Mon Sep 17 00:00:00 2001
From: Fox Caminiti <fox@foxcam.net>
Date: Wed, 17 Aug 2022 23:41:08 -0400
Subject: undo and pen development

---
 undo.cpp | 82 ++++++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 49 insertions(+), 33 deletions(-)

(limited to 'undo.cpp')

diff --git a/undo.cpp b/undo.cpp
index 3d70d49..e288784 100644
--- a/undo.cpp
+++ b/undo.cpp
@@ -1,5 +1,16 @@
 // get ready for some MLG...
 
+// The undo system currently works in two layers: a lower-level structless
+// stack that records "actions" and a higher-level array of "entries" that
+// bundle actions together. An action can either record a single change to a
+// specific memory address or a shift of pointers. Entries are what the user
+// sees and can contain multiple actions (i.e. adding a source changes the
+// value of the string and the increment of how many sources there are).
+// Entries are allowed to call functions in case there's something that can't
+// be incorporated into this memory model (i.e. deallocating libav contexts
+// when a layer's creation is undone), though they should be used only
+// when necessary.
+
 // These get four things pushed together: the address of what's being
 // changed, what type the data is, the original data, and the type again.
 // The type is encoded twice so we always know how big the data is whether
@@ -92,18 +103,19 @@ void Action_Change_Commit(memory *Memory, void *DataAddress, void *OriginalData,
     *(action_change_type *)Data = ActionChange;
 }
 
-void Action_Entry_Begin(memory *Memory, action_entry_type Type, char *Name)
-{
-    Memory->Action.Entry[Memory->Action.Index].Name = Name;
-    Memory->Action.Entry[Memory->Action.Index].Type = Type;
-}
-
-void Action_Entry_Begin2(memory *Memory, action_entry_type Type, char *Name, char *Name2)
+// This is only called when we're certain the action is going to be taken.
+void Action_Entry_Commit(memory *Memory, action_entry_type Type, char *Name)
 {
+    // We need to at least clear NumberOfActions in case this index is being reused.
+    Memory->Action.Entry[Memory->Action.Index] = {};
     Memory->Action.Entry[Memory->Action.Index].Name = Name;
     Memory->Action.Entry[Memory->Action.Index].Type = Type;
-    Memory->Action.Entry[Memory->Action.Index + 1].Name = Name2;
-    Memory->Action.Entry[Memory->Action.Index + 1].Type = Type;
+    // Effectively deletes entries in front if we're beginning out of an undo.
+    // It wouldn't be all that much more difficult to support branched undoing
+    // now that I think about it... (would anyone use it though?)
+    if (Memory->Action.Index != Memory->Action.NumberOfEntries) {
+        Memory->Action.NumberOfEntries = Memory->Action.Index;
+    }
 }
 
 void Action_Entry_SetPointer(memory *Memory, void *Data)
@@ -247,35 +259,39 @@ void Action_Change_Redo(memory *Memory) {
 }
 
 void Action_Undo(memory *Memory) {
-    Memory->Action.Index--;
-    action_entry Entry = Memory->Action.Entry[Memory->Action.Index];
-    switch (Entry.Type)
-    {
-        case action_entry_layerinit:
+    if (Memory->Action.Index != 0) {
+        Memory->Action.Index--;
+        action_entry Entry = Memory->Action.Entry[Memory->Action.Index];
+        switch (Entry.Type)
         {
-            AV_Dealloc((av_info *)*(ptrsize *)Entry.ExtraPointer);
-            *(ptrsize *)Entry.ExtraPointer = 0x0;   // what actually dereferences the pointer
-        } break;
-        case action_entry_default:
-        {
-        } break;
+            case action_entry_layerinit:
+            {
+                AV_Dealloc((av_info *)*(ptrsize *)Entry.ExtraPointer);
+                *(ptrsize *)Entry.ExtraPointer = 0x0;   // what actually dereferences the pointer
+            } break;
+            case action_entry_default:
+            {
+            } break;
+        }
+        for (int i = 0; i < Entry.NumberOfActions; i++)
+            Action_Change_Undo(Memory);
     }
-    for (int i = 0; i < Entry.NumberOfActions; i++)
-        Action_Change_Undo(Memory);
 }
 
 void Action_Redo(memory *Memory) {
-    action_entry Entry = Memory->Action.Entry[Memory->Action.Index];
-    switch (Entry.Type)
-    {
-        case action_entry_layerinit:
+    if (Memory->Action.Index != Memory->Action.NumberOfEntries) {
+        action_entry Entry = Memory->Action.Entry[Memory->Action.Index];
+        switch (Entry.Type)
         {
-        } break;
-        case action_entry_default:
-        {
-        } break;
+            case action_entry_layerinit:
+            {
+            } break;
+            case action_entry_default:
+            {
+            } break;
+        }
+        for (int i = 0; i < Entry.NumberOfActions; i++)
+            Action_Change_Redo(Memory);
+        Memory->Action.Index++;
     }
-    for (int i = 0; i < Entry.NumberOfActions; i++)
-        Action_Change_Redo(Memory);
-    Memory->Action.Index++;
 }
-- 
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