Collapse the split grid to the rows its month spans (#162)

app/src/main/java/de/jeanlucmakiola/calendula/ui/common/CalendarTransitions.kt

@@ -83,8 +83,10 @@ fun calendarSlideTransition(
         initialContentExit =
             slideOutHorizontally(spec) { w -> -dir * w / SLIDE_TRAVEL_DIVISOR } + fadeOut(fadeSpec),
         // AnimatedContent clips to the animating container by default, which
-        // shears the pages against the viewport edge as they pass. There is no
-        // size change here to contain — both pages are the same grid.
+        // shears the pages against the viewport edge as they pass. Left off even
+        // where the two pages differ in height — the split grid stands as many
+        // rows as its month spans (#162) — since a page sliding out over the row
+        // below it reads as travel, and the shear reads as a fault.
         sizeTransform = SizeTransform(clip = false),
     )
 }

app/src/main/java/de/jeanlucmakiola/calendula/ui/month/MonthScreen.kt

@@ -1141,10 +1141,10 @@ private val MONTH_EXPAND_THRESHOLD = 48.dp
  * lists whatever day is selected — and a downward drag trades the pane away for
  * the full paged grid, an upward one brings it back (#53).
  *
- * The grid slides between months like the paged style, which it can only do
- * because it always reserves [SPLIT_GRID_ROWS] rows. Sized to its own month it
- * stood 4–6 rows tall, so every swipe shunted the pane up or down by a row on
- * top of swapping the grid — the pane now holds still and only the grid moves.
+ * The grid slides between months like the paged style, and stands only as many
+ * rows tall as its own month spans (#162). A swipe between a five-row month and
+ * a six-row one therefore moves the pane by a row as well as swapping the grid;
+ * the row it hands back is worth more to the pane than a still edge is.
  *
  * Expansion is deliberately **not** a stored preference. It is a way to look at
  * the month you are on, not a fourth style; persisted, someone would expand it
@@ -1441,13 +1441,6 @@ private val SPLIT_DOT_SIZE = 5.dp
 // the paged grid's lanes, so the two caps have to be the same number or a dot
 // would have no bar to become (#53).
 
-/**
- * Rows the split grid always reserves — the most any month needs. A month that
- * fits in fewer pads the remainder with blank rows rather than shrinking, which
- * is what lets the pane below hold still from month to month.
- */
-private const val SPLIT_GRID_ROWS = 6
-
 /**
  * The expand handle: M3's drag-handle pill (32×4dp), in a row tall enough to be a
  * comfortable tap target on its own.
@@ -1460,6 +1453,11 @@ private val SPLIT_HANDLE_ROW_HEIGHT = 24.dp
  * The split style's grid (#53): the month compressed to day numbers and event
  * dots, with the selected day listed underneath by [SplitDayPane].
  *
+ * Only the rows the month actually spans. It used to pad every month out to six
+ * so the pane below held still from page to page, but a row is a sixth of the
+ * grid and a third of what the pane gets to show — too much to leave blank on
+ * the months that don't need it (#162).
+ *
  * Tapping selects rather than drilling into the Day view — the pane is the
  * answer to "what's on this day", so opening a whole screen for it would defeat
  * the layout. The full Day view stays one tap away on the pane's date header.
@@ -1518,12 +1516,6 @@ internal fun SplitMonthGrid(
                 }
             }
         }
-        // Hold the grid at a constant height whatever shape the month is, so the
-        // pane beneath it doesn't move as you page and one month can slide over
-        // another without a height change under it.
-        repeat(SPLIT_GRID_ROWS - state.weeks.size) {
-            Spacer(Modifier.fillMaxWidth().height(SPLIT_ROW_HEIGHT))
-        }
     }
 }