Breaking Down Full Scan Heatmap: Precursor M/z Line

Full scan heatmap: precursor m/z line disappears when zoomed out

When viewing proteomics data in full scan heatmaps, a subtle but telling glitch reveals itself: the precursor m/z marker vanishes when the m/z axis is zoomed wide. This line, meant to anchor your eye to the starting point of detection, fades into invisibility because its width - measured in m/z data units - becomes too narrow for clear rendering at low zoom. Without a fallback visual cue, ZedGraph’s rendering engine drops the box entirely, leaving a blank gap where context once lived.

The core issue lies in how ion mobility data is scaled. At wide views, the extraction box occupies barely enough space to stay visible - smaller than the minimum display buffer - triggering a complete omission. The box’s border, absent any 1-pixel safeguard, disappears with the line itself.

Here is the deal: the precursor mark doesn’t vanish - it just stops being seen, creating blind spots in data interpretation.

• Precursor m/z is visually represented by a thin extraction box, designed to be clear but fragile at wide zooms.
• At full scan views, the box shrinks below ZedGraph’s rendering threshold, disappearing without fallback.
• No pixel buffer or line override means the line vanishes completely, not just dimmed.
• This isn’t a bug in the data - it’s a limitation in how wide-zoom scaling handles tiny structural markers.
• Adding