Histogram AudioLevels accepts frames too narrow for audio bars

[msg7086]

> Analysis attribution: This issue analysis was created by Codex GPT.
> The GitHub user who submits this issue does not claim authorship of the analysis.

Finding

• Finding ID: B11-histogram-audio-levels-width
• Status: Reproduced defect
• Severity: Medium
• Affected component: Histogram AudioLevels
• Source location: avs_core/filters/histogram.cpp:240-253 and 287-301

Summary

Construction does not verify that the frame can hold required audio bars and labels; runtime bar width can become zero.

Affected Code

const int w = src->GetRowSize();
const int channels = vi.AudioChannels();

int bar_w = 60;
int total_width = (1+channels*2)*bar_w;

if (total_width > w) {
  bar_w = ((w / (1+channels*2)) / 4)* 4;
}
total_width = (1+channels*2)*bar_w;

Correct Behavior

Reject insufficient geometry at construction before any bar width can become non-positive.

Reproduction

Construct AudioLevels for an 8x32 YV12 frame with two audio channels.

Observed Result

observed: construction succeeds
expected: AvisynthError

Impact

Unsupported geometry reaches rendering calculations.

Validation Criteria

Too-narrow frames fail; minimum legal dimensions render nonzero bars.

Version and Environment

• AviSynthPlus revision: 815780226951f95dfc1fc74f1df90ef98824fcf5
• Platform and compiler: Linux x86_64 / Clang 22 debug
• CPU features used: host-default build.