Viewport shift on offset recalc - #812
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hannesa2 wants to merge 2 commits into
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The pan is stored in the touch matrix as a pixel translation, while the value-to-pixel scale is derived from the content rect. Resizing the content rect therefore makes the same pixel translation denote a different value, sliding the visible range. This is most visible after a zoom gesture: BarLineChartTouchListener defers chart.calculateOffsets() to ACTION_UP, so a y-zoom that widens the y-axis labels resizes the content rect only once the gesture ends, and the chart jumps sideways. The same happens when a fling settles, via computeScroll(). Scale the translation by the same ratio as the content rect so the visible range survives the resize. The visible extent is unaffected: it is (axis range / touch scale), which does not depend on the content width.
Adds two instrumented tests covering the viewport preservation fix in ViewPortHandler.restrainViewPort (PR #811). These must run on a device because the library's JVM unit tests stub android.graphics and cannot exercise the real Matrix math the fix depends on. The first test reproduces a real-world scenario: deeply zoomed/panned viewport, then content rect resize (from y-axis label growth). It verifies the visible x-range is preserved and reconstructs the pre-fix behavior to show it would shift ~83 x-units on a 3600-unit range. The second test asserts the pan ratios (transX/contentWidth, transY/contentHeight) are preserved across the resize. Also updates chartLib/build.gradle.kts to add androidTest dependencies.
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It's just a copy of #812 to see if CI is working properly