Re: Strange autoscaling with rgbimage and inverted yranges

On Friday, 11 September 2020 22:51:03 PDT Ethan A Merritt wrote:

> I _think_ that the problem involves this macro in axis.h
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> /* Simplest form of autoscaling (no check on autoscale constraints).
>  * Used by refresh_bounds() and refresh_3dbounds().
>  * Used also by autoscale_boxplot.
>  */
> #define autoscale_one_point(axis, x) do {\
>     if (axis->set_autoscale & AUTOSCALE_MIN && x < axis->min) \
>         axis->min = x; \
>     if (axis->set_autoscale & AUTOSCALE_MAX && x > axis->max) \
>         axis->max = x; \
>     } while (0);
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> as called from plot2d.c:refresh_bounds() when zooming volatile data.
> 
> Note that the macro does not consider the case of reversed axes.
> Adding a test for (axis->min < axis->max) seems to make your
> test case work.   See attached patch.

Better patch (but still not fully correct)

	Ethan

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diff --git a/src/axis.h b/src/axis.h
index a89800800..ed2e43973 100644
--- a/src/axis.h
+++ b/src/axis.h
@@ -404,10 +404,12 @@ extern struct axis THETA_AXIS;
  * Used also by autoscale_boxplot.
  */
 #define autoscale_one_point(axis, x) do {\
-    if (axis->set_autoscale & AUTOSCALE_MIN && x < axis->min) \
-	axis->min = x; \
-    if (axis->set_autoscale & AUTOSCALE_MAX && x > axis->max) \
-	axis->max = x; \
+    if (!(axis->range_flags & RANGE_IS_REVERSED)) { \
+	if (axis->set_autoscale & AUTOSCALE_MIN && x < axis->min) \
+	    axis->min = x; \
+	if (axis->set_autoscale & AUTOSCALE_MAX && x > axis->max) \
+	    axis->max = x; \
+	} \
     } while (0);
 
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