Region picker: HDR preview via D3D11 + ImGui, no more GDI

The drag-to-select picker now freezes the app's own capture texture and
presents it on a second scRGB FP16 swapchain with its own ImGui context,
so HDR desktops preview at their true nit values (8-bit SDR captures are
viewed through an _SRGB SRV). Same gestures and return contract as
before; the call site waits for a post-hide capture frame so the frozen
frame excludes the HDRScopes window. Drops msimg32. Font building is
shared with the main window via util/UiFonts.h. Suggested by Kaldaien.

Also fixed: retargeting between same-resolution HDR/SDR outputs kept the
old-format capture texture, so CopyResource silently failed and the
scopes showed the previous monitor's last frame.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: Shadetail

CHANGELOG.md

@@ -6,6 +6,16 @@ so every release ships with a readable summary.
 
 ## v1.0.7 — 2026-09-06
 
+- The "Select region on screen (drag)" picker now shows the frozen screen in
+  true HDR: it draws the app's own capture on an scRGB swapchain instead of
+  taking a GDI screenshot, which could only ever be SDR (and tone-mapped HDR
+  desktops into the bargain). Same gestures as before — drag to select,
+  release / Enter to confirm, Esc / right-click to cancel. Thanks to Kaldaien
+  (Special K / SKIV) for pointing out the GDI path and suggesting the
+  D3D11 route.
+- Fixed: switching the captured monitor between an HDR and an SDR output of
+  the same resolution left the scopes (and now the picker) showing the old
+  monitor's last frame until the capture was re-created.
 - The top readout can now also show the average luminance of the scoped
   region — the mean Rec.709 luminance of every pixel, in nits, i.e. the
   frame's overall light level (what SKIV's details panel calls Avg

CMakeLists.txt

@@ -50,7 +50,7 @@ add_executable(HDRScopes WIN32
 target_include_directories(HDRScopes PRIVATE src resources)
 target_link_libraries(HDRScopes PRIVATE
     imgui
-    d3d11 dxgi d3dcompiler dxguid dwmapi msimg32 winmm winhttp shell32
+    d3d11 dxgi d3dcompiler dxguid dwmapi winmm winhttp shell32
 )
 target_compile_definitions(HDRScopes PRIVATE UNICODE _UNICODE NOMINMAX WIN32_LEAN_AND_MEAN)
 

README.md

@@ -87,9 +87,10 @@ need that.
 <img align="right" width="260" src="docs/img/controls.png" alt="Controls popup">
 
 - **Controls** (top-right button) opens the settings popup: capture source
-  (monitor / window / dragged screen region), quality, and per-panel scope
-  options. Rest the mouse on any control for an explanation (tooltips can be
-  turned off under Preferences); right-click any control to reset just it.
+  (monitor / window / dragged screen region — the drag picker previews the
+  frozen screen in true HDR), quality, and per-panel scope options. Rest the
+  mouse on any control for an explanation (tooltips can be turned off under
+  Preferences); right-click any control to reset just it.
 - **Layouts** — the `1 / 2 / 4` buttons switch layout presets; each panel has
   a scope picker. Right-click `2` or `4` (or toggle Controls > Layout > "Stack
   panels vertically") to flip the multi-panel layouts between side-by-side and

docs/ARCHITECTURE.md

@@ -20,6 +20,11 @@ probe). `ScopeFactory` + `ScopePanel` host the 1/2/4-up layout.
   `settings.ini` next to the exe — local-first/portable — falling back to
   `%LOCALAPPDATA%\HDRScopes` when the exe's folder isn't writable; a pre-1.0.1
   file there still loads and migrates on first save.
+- `capture/RegionPicker` is the drag-to-select region picker: a topmost popup
+  over the captured output with its own scRGB FP16 swapchain and a second
+  ImGui context on the app's D3D11 device (no GDI). The frozen frame is a
+  copy of `CaptureSource`'s texture, so on HDR outputs it is shown at its
+  true nit values (8-bit SDR captures are viewed through an `_SRGB` SRV).
 - `util/SdrWhite` queries the Windows SDR-white level.
 - `util/UpdateCheck` is the startup update check: a background WinHTTP GET of
   `github.com/<repo>/releases/latest` with redirects disabled — the newest

src/capture/CaptureSource.cpp

@@ -166,7 +166,15 @@ void CaptureSource::ReleaseDuplicator() {
 }
 
 bool CaptureSource::EnsureTexture(UINT w, UINT h, DXGI_FORMAT fmt) {
-    if (tex_ && width_ == w && height_ == h && format_ == fmt) return true;
+    // Compare against the texture's own description, not format_: a retarget
+    // rewrites format_ from the new duplicator before the first frame arrives,
+    // so an HDR<->SDR switch between same-resolution outputs used to keep the
+    // old-format texture and every CopyResource into it silently failed.
+    if (tex_) {
+        D3D11_TEXTURE2D_DESC cur = {};
+        tex_->GetDesc(&cur);
+        if (cur.Width == w && cur.Height == h && cur.Format == fmt) return true;
+    }
     tex_.Reset();
     srv_.Reset();
 
@@ -231,6 +239,7 @@ bool CaptureSource::AcquireFrame(UINT timeoutMs) {
             if (EnsureTexture(sdesc.Width, sdesc.Height, sdesc.Format)) {
                 context_->CopyResource(tex_.Get(), srcTex.Get());
                 hasFrame_ = true;
+                ++frameSerial_;
             }
         }
     }

src/capture/CaptureSource.h

@@ -38,6 +38,12 @@ class CaptureSource {
     bool IsHDR() const { return isHDR_; }
     DXGI_FORMAT Format() const { return format_; }
     bool HasFrame() const { return hasFrame_; }
+    // A duplicator exists for the selected output. After a failed retarget the
+    // previous output's frame is still held (HasFrame stays true) but not live.
+    bool IsLive() const { return dup_ != nullptr; }
+    // Bumps each time a new desktop frame is copied (cursor-only updates don't
+    // count), so callers can tell a genuinely fresh frame from a reused one.
+    UINT64 FrameSerial() const { return frameSerial_; }
 
     // Enumerate outputs for the picker UI. Returns count; fills names/rects.
     struct OutputInfo { std::wstring name; RECT rect; bool hdr; int index; };
@@ -64,6 +70,7 @@ class CaptureSource {
     bool  isHDR_ = false;
     bool  hasFrame_ = false;
     bool  frameHeld_ = false;
+    UINT64 frameSerial_ = 0;
     int   curOutputIndex_ = 0;
     ULONGLONG lastDupAttemptMs_ = 0;
 };