Per-monitor DPI scaling for the whole UI (v1.0.2)

The window must be per-monitor DPI aware for Desktop Duplication, so the
UI scales itself: fonts and style rebuild from the window DPI (crisp
bitmap font at 1x, Consolas at scaled sizes), WM_DPICHANGED rescales
live between frames, and all fixed pixel sizes - widths, buttons, strip,
readout, overlay label offsets, scope margins, drag hit targets - follow
UiScale(). Readout dodges the button strip and panel combos when they
would collide; the controls popup re-snaps on scale changes and clamps
to the window height. HDRSCOPES_UISCALE env overrides for testing.

Reviewed by Codex (gpt-5.6-sol): its fixes (sub-1x font scaling,
readout plate scaling, histogram/waveform overlay offsets, ref-line
drag tolerance) are included, plus fixes for its findings (rescale
ordering, popup re-snap, left-side collision, top reservation).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Shadetail

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.20)
-project(HDRScopes VERSION 1.0.1 LANGUAGES CXX)
+project(HDRScopes VERSION 1.0.2 LANGUAGES CXX)
 if(MSVC)
     enable_language(RC)
 endif()

src/main.cpp

@@ -84,8 +84,9 @@ void CIEScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s) {
 }
 
 void CIEScope::DrawControls(Settings& s) {
+    const float u = UiScale();
     const char* diags[] = { "xy (1931)", "u'v' (1976)" };
-    ImGui::SetNextItemWidth(150); ImGui::Combo("Diagram", &s.cieDiagram, diags, 2);
+    ImGui::SetNextItemWidth(150 * u); ImGui::Combo("Diagram", &s.cieDiagram, diags, 2);
     UiReset(s.cieDiagram, UiDefaults().cieDiagram);
     UiTip("xy (1931) is the classic horseshoe diagram; u'v' (1976) spaces colors "
           "more perceptually evenly.");
@@ -106,7 +107,7 @@ void CIEScope::DrawControls(Settings& s) {
     UiTip("Outline the outermost chromaticity excursions - the source's actual "
           "gamut footprint - even where the trace is too faint to see.");
     if (s.cieExtents) {
-        ImGui::SameLine(); ImGui::SetNextItemWidth(110);
+        ImGui::SameLine(); ImGui::SetNextItemWidth(110 * u);
         ImGui::SliderFloat("##exop", &s.cieExtentsOpacity, 0.0f, 1.0f, "opacity %.2f");
         UiReset(s.cieExtentsOpacity, UiDefaults().cieExtentsOpacity);
     }

src/scope/CIEScope.cpp

@@ -124,6 +124,7 @@ double HistogramScope::ScreenXToNits(float x, const ScopeFrame& f, const Setting
 
 void HistogramScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s) {
     const float top = f.graphP0.y, bot = f.graphP1.y, left = f.graphP0.x, right = f.graphP1.x;
+    const float u = UiScale();
     const ImVec4 gc(s.graticuleColor.x, s.graticuleColor.y, s.graticuleColor.z, s.graticuleOpacity);
     const ImU32 colMajor = ImGui::GetColorU32(gc);
     const ImU32 colText = ImGui::GetColorU32(ImVec4(0.82f, 0.82f, 0.82f, std::max(0.5f, s.graticuleOpacity)));
@@ -137,7 +138,7 @@ void HistogramScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings&
         if (dec < 10000.0) for (int m = 2; m <= 9; ++m) {
             double n = dec * m; if (n > 10000.0) break;
             float mx = NitsToScreenX(n, f, s);
-            if (inX(mx)) dl->AddLine(ImVec2(mx, bot - 12.0f), ImVec2(mx, bot), colMajor, 1.0f);
+            if (inX(mx)) dl->AddLine(ImVec2(mx, bot - 12.0f * u), ImVec2(mx, bot), colMajor, 1.0f);
         }
     }
     dl->PopClipRect();
@@ -146,7 +147,7 @@ void HistogramScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings&
         char lab[16];
         if (dec >= 1000.0) snprintf(lab, sizeof(lab), "%gk", dec / 1000.0); else snprintf(lab, sizeof(lab), "%g", dec);
         ImVec2 ts = ImGui::CalcTextSize(lab);
-        dl->AddText(ImVec2(x - ts.x * 0.5f, bot + 4.0f), colText, lab);
+        dl->AddText(ImVec2(x - ts.x * 0.5f, bot + 4.0f * u), colText, lab);
     }
 
     // Nit value of the axis position under the cursor, attached to the cursor.
@@ -155,8 +156,8 @@ void HistogramScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings&
         char lab[32];
         FormatNits(std::clamp(ScreenXToNits(io.MousePos.x, f, s), 0.0, 10000.0), lab, sizeof(lab));
         ImVec2 ts = ImGui::CalcTextSize(lab);
-        ImVec2 tp(io.MousePos.x + 14.0f, io.MousePos.y - ts.y * 0.5f);
-        if (tp.x + ts.x > right) tp.x = io.MousePos.x - ts.x - 10.0f;
+        ImVec2 tp(io.MousePos.x + 14.0f * u, io.MousePos.y - ts.y * 0.5f);
+        if (tp.x + ts.x > right) tp.x = io.MousePos.x - ts.x - 10.0f * u;
         tp.y = std::clamp(tp.y, top, bot - ts.y);
         dl->AddText(ImVec2(tp.x + 1, tp.y + 1), IM_COL32(0, 0, 0, 200), lab);
         dl->AddText(tp, IM_COL32(235, 235, 235, 230), lab);
@@ -181,8 +182,9 @@ void HistogramScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings&
 }
 
 void HistogramScope::DrawControls(Settings& s) {
+    const float u = UiScale();
     const char* modes[] = { "LRGB rows", "Overlay RGB", "Luma" };
-    ImGui::SetNextItemWidth(160); ImGui::Combo("Mode", &s.histoMode, modes, 3);
+    ImGui::SetNextItemWidth(160 * u); ImGui::Combo("Mode", &s.histoMode, modes, 3);
     UiReset(s.histoMode, UiDefaults().histoMode);
     UiTip("LRGB rows: four stacked bands (luma, R, G, B). Overlay RGB: the channels "
           "drawn over each other in one band. Luma: a single luminance band.");
@@ -193,7 +195,7 @@ void HistogramScope::DrawControls(Settings& s) {
             ImGui::PushID(i + 100);
             ImVec4 c = s.histoChannelEnabled[i] ? onCol[i] : ImVec4(0.2f, 0.2f, 0.2f, 1);
             ImGui::PushStyleColor(ImGuiCol_Button, c); ImGui::PushStyleColor(ImGuiCol_ButtonHovered, c); ImGui::PushStyleColor(ImGuiCol_ButtonActive, c);
-            if (ImGui::Button(names[i], ImVec2(26, 26))) s.histoChannelEnabled[i] = !s.histoChannelEnabled[i];
+            if (ImGui::Button(names[i], ImVec2(26 * u, 26 * u))) s.histoChannelEnabled[i] = !s.histoChannelEnabled[i];
             UiReset(s.histoChannelEnabled[i], true);
             ImGui::PopStyleColor(3); ImGui::PopID(); if (i < 2) ImGui::SameLine();
         }
@@ -209,7 +211,7 @@ void HistogramScope::DrawControls(Settings& s) {
     float lg = std::log10(gmin), hg = std::log10(gmax);
     float t = (std::log10(std::clamp(s.histoGain, gmin, gmax)) - lg) / (hg - lg);
     int bri = (int)(t * 100.0f + 0.5f);
-    ImGui::SetNextItemWidth(180);
+    ImGui::SetNextItemWidth(180 * u);
     if (ImGui::SliderInt("Brightness", &bri, 0, 100))
         s.histoGain = std::pow(10.0f, lg + (bri / 100.0f) * (hg - lg));
     UiReset(s.histoGain, UiDefaults().histoGain);

src/scope/HistogramScope.cpp

@@ -1,5 +1,6 @@
 #include "scope/ScopePanel.h"
 #include "scope/ScopeFactory.h"
+#include "util/UiReset.h"
 #include <algorithm>
 #include <cmath>
 
@@ -19,10 +20,12 @@ void ScopePanel::Draw(int index, const ImVec2& panelP0, const ImVec2& panelP1,
     // Compute the histogram for this frame.
     scope_->Compute(input, s);
 
-    // Lay out the graph rect inside the panel (reserve margins).
+    // Lay out the graph rect inside the panel (reserve margins). Scopes return
+    // margins in 1x px; scale here so label room tracks the UI scale.
     Margins m = scope_->GetMargins(s);
-    ImVec2 g0(panelP0.x + m.l, panelP0.y + m.t);
-    ImVec2 g1(panelP1.x - m.r, panelP1.y - m.b);
+    const float mu = UiScale();
+    ImVec2 g0(panelP0.x + m.l * mu, panelP0.y + m.t * mu);
+    ImVec2 g1(panelP1.x - m.r * mu, panelP1.y - m.b * mu);
     float gw = g1.x - g0.x, gh = g1.y - g0.y;
     float aspect = scope_->AspectRatio();
     if (aspect > 0.0f && gw > 0 && gh > 0) {

src/scope/ScopePanel.cpp

@@ -96,6 +96,7 @@ void VectorScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s)
 }
 
 void VectorScope::DrawControls(Settings& s) {
+    const float u = UiScale();
     int enc = s.vectorPQ ? 1 : 0;
     if (ImGui::Combo("Encoding", &enc, "Rec.709 (SDR)\0PQ (HDR)\0")) s.vectorPQ = (enc == 1);
     UiReset(s.vectorPQ, UiDefaults().vectorPQ);
@@ -130,7 +131,7 @@ void VectorScope::DrawControls(Settings& s) {
     UiTip("Outline the outermost chroma excursions - the source's actual color "
           "footprint - even where the trace is too faint to see.");
     if (s.vectorExtents) {
-        ImGui::SameLine(); ImGui::SetNextItemWidth(110);
+        ImGui::SameLine(); ImGui::SetNextItemWidth(110 * u);
         ImGui::SliderFloat("##exop", &s.vectorExtentsOpacity, 0.0f, 1.0f, "opacity %.2f");
         UiReset(s.vectorExtentsOpacity, UiDefaults().vectorExtentsOpacity);
     }

src/scope/VectorScope.cpp

@@ -262,6 +262,7 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
     const float top = f.graphP0.y, bot = f.graphP1.y;
     const float left = f.graphP0.x, right = f.graphP1.x;
     const float graphW = right - left, graphH = bot - top;
+    const float u = UiScale();
     auto inRange = [&](float y) { return y >= top - 0.5f && y <= bot + 0.5f; };
 
     const ImVec4 gc = ImVec4(s.graticuleColor.x, s.graticuleColor.y, s.graticuleColor.z, s.graticuleOpacity);
@@ -284,7 +285,7 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
         for (int m = 2; m <= 9; ++m) {
             double n = dec * m; if (n > 10000.0) break;
             float my = NitsToScreenY(n, f, s);
-            if (inRange(my)) dl->AddLine(ImVec2(left - 20.0f, my), ImVec2(left, my), colMinor, 1.0f);
+            if (inRange(my)) dl->AddLine(ImVec2(left - 20.0f * u, my), ImVec2(left, my), colMinor, 1.0f);
         }
     }
 
@@ -298,7 +299,7 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
         else               snprintf(lab, sizeof(lab), "%g", dec);
         ImVec2 ts = ImGui::CalcTextSize(lab);
         float ly = std::max(y - ts.y * 0.5f, top);
-        dl->AddText(ImVec2(left - 4.0f - ts.x, ly), colText, lab);
+        dl->AddText(ImVec2(left - 4.0f * u - ts.x, ly), colText, lab);
     }
 
     // Extents white envelope line (style 1).
@@ -347,9 +348,9 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
         // Label sits inside the plot at the left edge, matching the graticule
         // labels' side (those live outside; keeping this inside avoids overlap).
         char lab[32]; snprintf(lab, sizeof(lab), "%.0f", s.refLines[i].nits);
-        dl->AddText(ImVec2(left + 6.0f, y - 14.0f), col, lab);
+        dl->AddText(ImVec2(left + 6.0f * u, y - ImGui::GetFontSize() - 1.0f * u), col, lab);
 
-        if (hovered && io.MouseClicked[0] && fabsf(io.MousePos.y - y) < 5.0f) draggingRef_ = (int)i;
+        if (hovered && io.MouseClicked[0] && fabsf(io.MousePos.y - y) < 5.0f * u) draggingRef_ = (int)i;
     }
     if (draggingRef_ >= 0) {
         if (io.MouseDown[0] && draggingRef_ < (int)s.refLines.size())
@@ -362,8 +363,8 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
         char lab[32];
         FormatNits(std::clamp(ScreenYToNits(io.MousePos.y, f, s), 0.0, 10000.0), lab, sizeof(lab));
         ImVec2 ts = ImGui::CalcTextSize(lab);
-        ImVec2 tp(io.MousePos.x + 14.0f, io.MousePos.y - ts.y * 0.5f);
-        if (tp.x + ts.x > right) tp.x = io.MousePos.x - ts.x - 10.0f;
+        ImVec2 tp(io.MousePos.x + 14.0f * u, io.MousePos.y - ts.y * 0.5f);
+        if (tp.x + ts.x > right) tp.x = io.MousePos.x - ts.x - 10.0f * u;
         tp.y = std::clamp(tp.y, top, bot - ts.y);
         dl->AddText(ImVec2(tp.x + 1, tp.y + 1), IM_COL32(0, 0, 0, 200), lab);
         dl->AddText(tp, IM_COL32(235, 235, 235, 230), lab);
@@ -393,6 +394,7 @@ void WaveformScope::DrawOverlay(ImDrawList* dl, const ScopeFrame& f, Settings& s
 }
 
 void WaveformScope::DrawControls(Settings& s) {
+    const float u = UiScale();
     ImGui::RadioButton("Luminance", &s.waveMode, 0);
     UiReset(s.waveMode, UiDefaults().waveMode);
     UiTip("One trace of overall brightness (luminance) per column."); ImGui::SameLine();
@@ -411,7 +413,7 @@ void WaveformScope::DrawControls(Settings& s) {
             ImGui::PushStyleColor(ImGuiCol_Button, c);
             ImGui::PushStyleColor(ImGuiCol_ButtonHovered, c);
             ImGui::PushStyleColor(ImGuiCol_ButtonActive, c);
-            if (ImGui::Button(names[i], ImVec2(26, 26))) s.channelEnabled[i] = !s.channelEnabled[i];
+            if (ImGui::Button(names[i], ImVec2(26 * u, 26 * u))) s.channelEnabled[i] = !s.channelEnabled[i];
             UiReset(s.channelEnabled[i], true);
             ImGui::PopStyleColor(3); ImGui::PopID();
             if (i < 2) ImGui::SameLine();
@@ -428,7 +430,7 @@ void WaveformScope::DrawControls(Settings& s) {
           "trace is too faint to see - as colored points or a thin envelope line.");
     if (s.waveExtents) {
         ImGui::SameLine();
-        ImGui::SetNextItemWidth(150);
+        ImGui::SetNextItemWidth(150 * u);
         const char* styles[] = { "Colored points", "White envelope line" };
         ImGui::Combo("##extstyle", &s.waveExtentsStyle, styles, 2);
         UiReset(s.waveExtentsStyle, UiDefaults().waveExtentsStyle);
@@ -440,7 +442,7 @@ void WaveformScope::DrawControls(Settings& s) {
             UiTip("Read every source pixel for the extents even when Quality samples "
                   "a coarser grid, so single-pixel peaks can't slip through.");
         }
-        ImGui::SetNextItemWidth(150);
+        ImGui::SetNextItemWidth(150 * u);
         ImGui::SliderFloat("Extents opacity", &s.waveExtentsOpacity, 0.0f, 1.0f, "%.2f");
         UiReset(s.waveExtentsOpacity, UiDefaults().waveExtentsOpacity);
     }
@@ -457,17 +459,17 @@ void WaveformScope::DrawControls(Settings& s) {
     UiTip("Smooth the trace across neighboring columns (Resolve-style low pass): "
           "exposure bands become easier to read, single-column spikes fade.");
     if (s.lowPass) {
-        ImGui::SameLine(); ImGui::SetNextItemWidth(120);
+        ImGui::SameLine(); ImGui::SetNextItemWidth(120 * u);
         ImGui::SliderFloat("Strength##lpa", &s.lowPassAmount, 0.0f, 1.0f, "%.2f");
         UiReset(s.lowPassAmount, UiDefaults().lowPassAmount);
     }
 
     // Reference lines: custom count, log drag (shift = 10x finer), thickness.
     ImGui::SeparatorText("Reference lines");
-    ImGui::SetNextItemWidth(120);
+    ImGui::SetNextItemWidth(120 * u);
     ImGui::SliderFloat("Thickness", &s.refLineThickness, 1.0f, 6.0f, "%.1f px");
     UiReset(s.refLineThickness, UiDefaults().refLineThickness);
-    ImGui::SetNextItemWidth(120);
+    ImGui::SetNextItemWidth(120 * u);
     ImGui::SliderFloat("Opacity##ref", &s.refLineOpacity, 0.0f, 1.0f, "%.2f");
     UiReset(s.refLineOpacity, UiDefaults().refLineOpacity);
     ImGuiIO& io = ImGui::GetIO();
@@ -481,7 +483,7 @@ void WaveformScope::DrawControls(Settings& s) {
         ImGui::SameLine();
         float v = (float)s.refLines[i].nits;
         float speed = io.KeyShift ? 0.02f : 0.5f; // hold Shift for 10x-finer control
-        ImGui::SetNextItemWidth(150);
+        ImGui::SetNextItemWidth(150 * u);
         if (ImGui::DragFloat("nits", &v, speed, 0.0f, 10000.0f, "%.2f", ImGuiSliderFlags_Logarithmic))
             s.refLines[i].nits = std::clamp((double)v, 0.0, 10000.0);
         UiReset(s.refLines[i].nits, defaultRef.nits);

src/scope/WaveformScope.cpp

@@ -10,6 +10,10 @@
 
 inline const Settings& UiDefaults() { static const Settings d; return d; }
 
+// Current UI scale (window DPI / 96). Fixed pixel sizes in UI code multiply by
+// this; fonts and style paddings are rebuilt in main.cpp's ApplyUiScale.
+inline float& UiScale() { static float s = 1.0f; return s; }
+
 inline bool UiResetClicked() {
     return ImGui::IsItemHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Right);
 }