Added issues 121, 122, 123

TO-DO-List.md

@@ -183,7 +183,6 @@ Contents:
    address so you don't have to go through and add them by hand.
  * When a local variable table item is double-clicked on, open the editor
    with that item selected and focused.
-
  * Support expressions.
    * Start with simple expressions, such as ORing of multiple constants
      or defining an offset as the difference between two symbols.
@@ -193,6 +192,7 @@ Contents:
      (instruction and data operands).  This is straightforward to manage
      within SourceGen, but can be difficult to generate for all cross-assemblers
      if the complexity gets too high.
+   * (See https://github.com/fadden/6502bench/issues/123 .)
  * Support multi-line editing for instructions.  Like what we do for data, but
    for code.  Not sure how often that will be useful, or how it will work
    for an arbitrary selection.  (A keyboard shortcut that rotates through
@@ -212,6 +212,14 @@ Contents:
  * "Navigate to last change" jumps to offset 0 for things like project
    property changes that don't have an offset.  Should probably jump
    to the previous change instead.
+ * Support a "struct" notion, possibly defined in external files, for things
+   like file headers, bitmaps, and parameter blocks.  (See
+   https://github.com/fadden/6502bench/issues/121 .)
+ * Add a notion of "fixed length" vs. "fixed endpoint" to the various bulk data
+   operands.  The idea is that the data needs to end at a specific point, like
+   an "align" directive but more arbitrary.  The distinction becomes important
+   if the generated code is modified and re-assembled.
+   (See https://github.com/fadden/6502bench/issues/122 .)
 
 ### Visualizations ###
 
@@ -306,7 +314,6 @@ Contents:
    firmware.  The branch is never taken; it just conceals an embedded
    instruction.  This causes an auto-label to be generated.  In generated
    source code the auto-label is output but never referenced.
-
  * Speculative code hinting.  A human can look at `a9 40 85 02 20 ed fd` and
    recognize 6502 code.  The computer should be able to manage it with a
    reasonable degree of success.  The result would need to be displayed in a