Files
CoopAllTheThings/tests/dpi_test.cpp
BlackMark d73b43ad0d Make the host per-monitor DPI aware and scale the ImGui overlay
The window sized itself to GetSystemMetrics(SM_CXSCREEN/CYSCREEN) but the
process was DPI-unaware, so on a scaled display (e.g. 4K @ 150%) Windows
handed us a virtualized resolution and bitmap-stretched the whole window up
to native -- softening the mirror, which is the tool's entire point.

Declare per-monitor-v2 awareness at startup so GetSystemMetrics/GetDpiForWindow
report true pixels. That alone would shrink the fixed-13px ImGui overlay to
crisp-but-tiny, so pair it with UI scaling: rebuild the default-font atlas at a
DPI-scaled SizePixels (crisp at the target size, unlike FontGlobalScale's
bitmap stretch) and ScaleAllSizes() the style. Net: same physical size as
before, now sharp.

- common/include/coop/dpi.hpp: pure DPI->scale math (uses USER_DEFAULT_SCREEN_DPI
  and a named kBaseFontPx, not bare 96/13 literals), with a zero fallback and
  clamping. Unit-tested by tests/dpi_test.cpp.
- imgui_layer: apply_dpi() at init from GetDpiForWindow; set_dpi() for runtime
  changes (rebuild atlas + reset/scale style + invalidate the DX11 font texture).
- d3d11_window: latch WM_DPICHANGED (honor the suggested rect), expose
  take_dpi_change(); main loop polls it and calls imgui.set_dpi() between frames.

The DPI math is unit-tested; the actual awareness + font rasterization + live
WM_DPICHANGED rescale are verified by hand.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-01 23:23:41 +02:00

53 lines
2.0 KiB
C++

// Unit test for the DPI -> UI scale math (common/include/coop/dpi.hpp): the 96-DPI baseline, common
// Windows scalings, the zero-DPI fallback, clamping at both ends, and the default-font pixel-size
// derivation. Pure math -- no window, no ImGui -- so it's the reasonably-testable slice of the
// per-monitor DPI feature (the actual awareness + font rasterization are verified by hand).
#include <cmath>
#include <cstdio>
#include "coop/dpi.hpp"
using namespace coop;
namespace
{
int g_failures = 0;
void check(bool ok, const char* what)
{
std::printf("%s %s\n", ok ? " ok:" : "FAIL:", what);
if (!ok)
{
++g_failures;
}
}
bool approx(float a, float b)
{
return std::fabs(a - b) < 1e-4f;
}
} // namespace
int main()
{
// Baseline and the common Windows display scalings.
check(approx(dpi_scale_from(96), 1.0f), "96 DPI -> 1.0 (100%)");
check(approx(dpi_scale_from(120), 1.25f), "120 DPI -> 1.25 (125%)");
check(approx(dpi_scale_from(144), 1.5f), "144 DPI -> 1.5 (150%)");
check(approx(dpi_scale_from(192), 2.0f), "192 DPI -> 2.0 (200%)");
// A zero / unknown DPI falls back to the 96 baseline (never 0 -> a zero-size font).
check(approx(dpi_scale_from(0), 1.0f), "0 DPI -> 1.0 fallback");
// Clamping: never below 100%, and capped at the max for an absurd report.
check(approx(dpi_scale_from(48), kMinUiScale), "48 DPI clamps up to the min UI scale");
check(approx(dpi_scale_from(100000), kMaxUiScale), "absurd DPI clamps to the max UI scale");
// Font size scales from the single named base constant, matching ImGui's 13px default at 100%.
check(approx(kBaseFontPx, 13.0f), "base font px is ImGui's 13px default");
check(approx(scaled_font_px(96), 13.0f), "font px at 100% == base");
check(approx(scaled_font_px(144), 19.5f), "font px at 150% == 13 * 1.5");
check(approx(scaled_font_px(0), kBaseFontPx), "font px at unknown DPI == base (fallback)");
std::printf(g_failures == 0 ? "PASS dpi_test\n" : "FAILED dpi_test (%d)\n", g_failures);
return g_failures == 0 ? 0 : 1;
}