Always show a minimum bars during startup

This is particularly more "good looking" when we boot with a pair that
doesn't have historical 1s OHLC and thus the fast chart is empty from
outset. In this case it's a lot nicer to be already zoomed to
a comfortable preset number of "datums in view" even when the history
isn't yet filled in.

Adjusts the chart display `Viz.default_view()` startup to explicitly
ensure this happens via the `do_min_bars=True` flag B)

piker/ui/_dataviz.py

@@ -1082,12 +1082,10 @@ class Viz(Struct):
         data_diff = last_datum - first_datum
         rl_diff = vr - vl
         rescale_to_data: bool = False
-        # new_uppx: float = 1
 
         if rl_diff > data_diff:
             rescale_to_data = True
             rl_diff = data_diff
-            new_uppx: float = data_diff / self.px_width()
 
         # orient by offset from the y-axis including
         # space to compensate for the L1 labels.
@@ -1097,14 +1095,28 @@ class Viz(Struct):
             offset = l1_offset
 
             if rescale_to_data:
+                new_uppx: float = data_diff / self.px_width()
                 offset = (offset / uppx) * new_uppx
 
         else:
             offset = (y_offset * step) + uppx*step
 
+        # NOTE: if we are in the midst of start-up and a bunch of
+        # widgets are spawning/rendering  concurrently, it's likely the
+        # label size above `l1_offset` won't have yet fully rendered.
+        # Here we try to compensate for that ensure at least a static
+        # bar gap between the last datum and the y-axis.
+        if (
+            do_min_bars
+            and offset <= (6 * step)
+        ):
+            offset = 6 * step
+
         # align right side of view to the rightmost datum + the selected
         # offset from above.
-        r_reset = (self.graphics.x_last() or last_datum) + offset
+        r_reset = (
+            self.graphics.x_last() or last_datum
+        ) + offset
 
         # no data is in view so check for the only 2 sane cases:
         # - entire view is LEFT of data
@@ -1129,7 +1141,6 @@ class Viz(Struct):
             else:
                 log.warning(f'Unknown view state {vl} -> {vr}')
                 return
-
         else:
             # maintain the l->r view distance
             l_reset = r_reset - rl_diff
@@ -1138,7 +1149,11 @@ class Viz(Struct):
             do_min_bars
             and (r_reset - l_reset) < min_bars_from_y
         ):
-            l_reset = r_reset - min_bars_from_y
+            l_reset = (
+                (r_reset + offset)
+                -
+                min_bars_from_y * step
+            )
 
         # remove any custom user yrange setttings
         if chartw._static_yrange == 'axis':
@@ -1152,7 +1167,6 @@ class Viz(Struct):
 
         if do_ds:
             view.interact_graphics_cycle()
-            view.interact_graphics_cycle()
 
     def incr_info(
         self,

piker/ui/_display.py

@@ -416,7 +416,9 @@ async def graphics_update_loop(
             ds.vlm_chart = vlm_chart
             ds.vlm_sticky = vlm_sticky
 
-        fast_chart.main_viz.default_view()
+        fast_chart.main_viz.default_view(
+            do_min_bars=True,
+        )
 
         # ds.hist_vars.update({
         #     'i_last_append': 0,
@@ -1456,7 +1458,9 @@ async def display_symbol_data(
             for fqsn, flume in feed.flumes.items():
 
                 # size view to data prior to order mode init
-                rt_chart.main_viz.default_view()
+                rt_chart.main_viz.default_view(
+                    do_min_bars=True,
+                )
                 rt_linked.graphics_cycle()
 
                 # TODO: look into this because not sure why it was
@@ -1467,7 +1471,9 @@ async def display_symbol_data(
                 # determine if auto-range adjustements should be made.
                 # rt_linked.subplots.pop('volume', None)
 
-                hist_chart.main_viz.default_view()
+                hist_chart.main_viz.default_view(
+                    do_min_bars=True,
+                )
                 hist_linked.graphics_cycle()
 
                 godwidget.resize_all()
@@ -1510,10 +1516,14 @@ async def display_symbol_data(
 
                 # default view adjuments and sidepane alignment
                 # as final default UX touch.
-                rt_chart.main_viz.default_view()
+                rt_chart.main_viz.default_view(
+                    do_min_bars=True,
+                )
                 await trio.sleep(0)
 
-                hist_chart.main_viz.default_view()
+                hist_chart.main_viz.default_view(
+                    do_min_bars=True,
+                )
                 hist_viz = hist_chart.get_viz(fqsn)
                 await trio.sleep(0)