Bug Description:

Scrolling the merge editor vertically can sometimes cause misalignments in scroll-sync between the vertically split panes.

Steps to Reproduce:

1. Open the 3-way merge editor with the Merge Editor (Dev): Open Merge Editor State from JSON command (which is available in the command palette, F1) using the following JSON:

   {
     "base": "1\n2\n3\n4\n5\na\n6\n7\n8\n9\n10",
     "input1": "1\n2\n3\n4\n5\n6\n7\n8\n9\n10",
     "input2": "1\n2\n3\n4\n5\na\nb\nc\nd\ne\nf\ng\n6\n7\n8\n9\n10",
     "result": "1\n2\n3\n4\n5\na\n6\n7\n8\n9\n10"
   }
   

   This corresponds to the following merge conflict:

   

2. Scroll the Left (!) pane vertically until the merge conflict is displayed at the top of the Left pane:

   

   Observe that, while the merge conflict is displayed at the top of each of the horizontally split panes now, the bottom (Result) pane displays the line 5 at the top. It would be expected that the merge conflict should be displayed at the top of the Result pane also in this case:

   

3. Scroll the Result (!) pane vertically until the merge conflict is displayed at the top of the Result pane:

   

   Observe that the merge conflict is no longer displayed at the top of each of the horizontally split panes in this case, contrary to what would have been expected.

4. Continue scrolling the Result pane vertically until the line a is displayed just near the top of the Result pane:

   

   Observe that the merge conflict is almost scrolled out of view in the horizontally split panes now, while it would be expected that all panes should be precisely aligned relative to the line a in this case:

   

Additional Information

I'm going to submit a fix.

• Operating System: all
• Theia Version: 1.68 (current master)