SkXPS: clean up SkConstexprMath

src/xps/SkXPSDevice.cpp

Index: src/xps/SkXPSDevice.cpp
diff --git a/src/xps/SkXPSDevice.cpp b/src/xps/SkXPSDevice.cpp
index aef9dc8baf8659b751c966becb167a9ccd3adcda..c7f03d33cd805c64646ce638418ab77a11b9967d 100644
--- a/src/xps/SkXPSDevice.cpp
+++ b/src/xps/SkXPSDevice.cpp
@@ -18,9 +18,9 @@
 #include <XpsObjectModel.h>
 #include <T2EmbApi.h>
 #include <FontSub.h>
+#include <limits>
 
 #include "SkColor.h"
-#include "SkConstexprMath.h"
 #include "SkData.h"
 #include "SkDraw.h"
 #include "SkEndian.h"
@@ -202,10 +202,10 @@ HRESULT SkXPSDevice::createXpsThumbnail(IXpsOMPage* page,
         "Could not create thumbnail generator.");
 
     SkTScopedComPtr<IOpcPartUri> partUri;
-    static const size_t size = SkTUMax<
-        SK_ARRAY_COUNT(L"/Documents/1/Metadata/.png") + SK_DIGITS_IN(pageNum),
-        SK_ARRAY_COUNT(L"/Metadata/" L_GUID_ID L".png")
-    >::value;
+    constexpr size_t size = SkTMax<size_t>(

[bungeman-skia, 2016/05/23 18:12:38]

Both parameters are size_t now, so it shouldn't need to be specified here.

[hal.canary, 2016/05/28 17:05:54]

Done.

+            SK_ARRAY_COUNT(L"/Documents/1/Metadata/.png")
+            + static_cast<size_t>(std::numeric_limits<unsigned>::digits10 + 1),

[bungeman-skia, 2016/05/23 18:12:38]

It's rather annoying that this indentation kinda hides where the two parameters
are. Maybe it makes sense to create a file local

template <typename T> static constexpr size_t sk_digits_in(T) {
    return static_cast<size_t>(std::numeric_limits<T>::digits10 + 1);
}

so that each parameter fits on one line (and also indicates intent). This also
fixes the issue where in the new code 'unsigned' (a manual inlining of
'decltype(pageNum)') is being used instead of 'pageNum'. 

[hal.canary, 2016/05/28 17:05:54]

Done.

+            SK_ARRAY_COUNT(L"/Metadata/" L_GUID_ID L".png"));
     wchar_t buffer[size];
     if (pageNum > 0) {
         swprintf_s(buffer, size, L"/Documents/1/Metadata/%u.png", pageNum);
@@ -229,8 +229,9 @@ HRESULT SkXPSDevice::createXpsThumbnail(IXpsOMPage* page,
 
 HRESULT SkXPSDevice::createXpsPage(const XPS_SIZE& pageSize,
                                    IXpsOMPage** page) {
-    static const size_t size = SK_ARRAY_COUNT(L"/Documents/1/Pages/.fpage")
-                             + SK_DIGITS_IN(fCurrentPage);
+    constexpr size_t size =
+        SK_ARRAY_COUNT(L"/Documents/1/Pages/.fpage")
+        + static_cast<size_t>(std::numeric_limits<unsigned>::digits10 + 1);
     wchar_t buffer[size];
     swprintf_s(buffer, size, L"/Documents/1/Pages/%u.fpage",
                              this->fCurrentPage);