Draw only visible part of the reflogs panel

Since the reflog can get very long, this saves some memory but especially some UI thread lag. In one of my repos I had over 11'000 reflog entries (I guess I should prune them more regularly...), and rendering them took ~600ms; since this happens on the UI thread, there was an annoying stall for half a second after every background fetch, for example.

Author: stefanhaller

pkg/gui/context/reflog_commits_context.go

@@ -26,9 +26,14 @@ func NewReflogCommitsContext(c *ContextCommon) *ReflogCommitsContext {
 },
 )
 
-getDisplayStrings := func(_ int, _ int) [][]string {
+getDisplayStrings := func(startIdx int, endIdx int) [][]string {
+commits := viewModel.GetItems()
+if startIdx >= len(commits) {
+return nil
+}
+
 return presentation.GetReflogCommitListDisplayStrings(
-viewModel.GetItems(),
+commits[startIdx:endIdx],
 c.State().GetRepoState().GetScreenMode() != types.SCREEN_NORMAL,
 c.Modes().CherryPicking.SelectedHashSet(),
 c.Modes().Diffing.Ref,
@@ -43,18 +48,20 @@ func NewReflogCommitsContext(c *ContextCommon) *ReflogCommitsContext {
 FilteredListViewModel: viewModel,
 ListContextTrait: &ListContextTrait{
 Context: NewSimpleContext(NewBaseContext(NewBaseContextOpts{
-View: c.Views().ReflogCommits,
-WindowName: "commits",
-Key: REFLOG_COMMITS_CONTEXT_KEY,
-Kind: types.SIDE_CONTEXT,
-Focusable: true,
-NeedsRerenderOnWidthChange: types.NEEDS_RERENDER_ON_WIDTH_CHANGE_WHEN_SCREEN_MODE_CHANGES,
+View: c.Views().ReflogCommits,
+WindowName: "commits",
+Key: REFLOG_COMMITS_CONTEXT_KEY,
+Kind: types.SIDE_CONTEXT,
+Focusable: true,
+NeedsRerenderOnWidthChange: types.NEEDS_RERENDER_ON_WIDTH_CHANGE_WHEN_SCREEN_MODE_CHANGES,
+NeedsRerenderOnHeightChange: true,
 })),
 ListRenderer: ListRenderer{
 list: viewModel,
 getDisplayStrings: getDisplayStrings,
 },
-c: c,
+c: c,
+renderOnlyVisibleLines: true,
 },
 }
 }