From 3d87ea91af766d99dffc17f233b35e941eeefaf1 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@qt.io>
Date: Tue, 2 Jul 2019 16:20:06 +0200
Subject: [PATCH] RHI/D3D11: Remove hard dependency on D3DCompiler library

Varying versions of the library may be available depending on build tool
chain or Windows version. Try to dynamically resolve the D3DCompile
function.

Fixes: QTBUG-76845
Change-Id: Ib7eb3b8c454e9c25731eb2ba9ba45e54fe3f1283
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
---
 src/gui/rhi/qrhid3d11.cpp | 21 ++++++++++++++++++++-
 src/gui/rhi/rhi.pri       |  2 +-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index eea2a13d8c..a8a490eb5c 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -39,6 +39,7 @@
 #include <QWindow>
 #include <QOperatingSystemVersion>
 #include <qmath.h>
+#include <private/qsystemlibrary_p.h>
 
 #include <d3dcompiler.h>
 #include <comdef.h>
@@ -3218,6 +3219,18 @@ static inline D3D11_BLEND_OP toD3DBlendOp(QRhiGraphicsPipeline::BlendOp op)
     }
 }
 
+static pD3DCompile resolveD3DCompile()
+{
+    for (const wchar_t *libraryName : {L"D3DCompiler_47", L"D3DCompiler_43"}) {
+        QSystemLibrary library(libraryName);
+        if (library.load()) {
+            if (auto symbol = library.resolve("D3DCompile"))
+                return reinterpret_cast<pD3DCompile>(symbol);
+        }
+    }
+    return nullptr;
+}
+
 static QByteArray compileHlslShaderSource(const QShader &shader, QShader::Variant shaderVariant, QString *error)
 {
     QShaderCode dxbc = shader.shader({ QShader::DxbcShader, 50, shaderVariant });
@@ -3255,9 +3268,15 @@ static QByteArray compileHlslShaderSource(const QShader &shader, QShader::Varian
         return QByteArray();
     }
 
+    static const pD3DCompile d3dCompile = resolveD3DCompile();
+    if (d3dCompile == nullptr) {
+        qWarning("Unable to resolve function D3DCompile()");
+        return QByteArray();
+    }
+
     ID3DBlob *bytecode = nullptr;
     ID3DBlob *errors = nullptr;
-    HRESULT hr = D3DCompile(hlslSource.shader().constData(), hlslSource.shader().size(),
+    HRESULT hr = d3dCompile(hlslSource.shader().constData(), hlslSource.shader().size(),
                             nullptr, nullptr, nullptr,
                             hlslSource.entryPoint().constData(), target, 0, 0, &bytecode, &errors);
     if (FAILED(hr) || !bytecode) {
diff --git a/src/gui/rhi/rhi.pri b/src/gui/rhi/rhi.pri
index d8607f1024..4297a5602b 100644
--- a/src/gui/rhi/rhi.pri
+++ b/src/gui/rhi/rhi.pri
@@ -40,7 +40,7 @@ win32 {
     SOURCES += \
         rhi/qrhid3d11.cpp
 
-    LIBS += -ld3d11 -ldxgi -ldxguid -ld3dcompiler
+    LIBS += -ld3d11 -ldxgi -ldxguid
 }
 
 # darwin {