Switch over to C++14, drop support for MSVC 2015

The main reason is that the current development version of Eigen requires C++14 to be enabled, so otherwise we can't compile with the latest Eigen.

If really needed, we can keep support for MSVC 2015 (please make your voice heard) but that would lock us out of a few features of C++14.

.github/workflows/ci.yml

@@ -394,7 +394,7 @@ jobs:
     - name: Build Python 3.12
       shell: bash
       run: |
-        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10
+        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10 --msvc-version=14.2
     - name: Test Python 3.12
       shell: bash
       run: |
@@ -408,7 +408,7 @@ jobs:
     - name: Build Python 3.11
       shell: bash
       run: |
-        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10
+        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10 --msvc-version=14.2
     - name: Test Python 3.11
       shell: bash
       run: |
@@ -422,7 +422,7 @@ jobs:
     - name: Build Python 3.10
       shell: bash
       run: |
-        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10
+        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10 --msvc-version=14.2
     - name: Test Python 3.10
       shell: bash
       run: |
@@ -436,7 +436,7 @@ jobs:
     - name: Build Python 3.9
       shell: bash
       run: |
-        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10
+        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10 --msvc-version=14.2
     - name: Test Python 3.9
       shell: bash
       run: |
@@ -450,7 +450,7 @@ jobs:
     - name: Build Python 3.8
       shell: bash
       run: |
-        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10
+        python makepanda/makepanda.py --git-commit=${{github.sha}} --outputdir=built --everything --no-eigen --python-incdir="$pythonLocation/include" --python-libdir="$pythonLocation/lib" --verbose --threads=4 --windows-sdk=10 --msvc-version=14.2
     - name: Test Python 3.8
       shell: bash
       run: |

README.md

@@ -52,7 +52,7 @@ Building Panda3D
 Windows
 -------
 
-You can build Panda3D with the Microsoft Visual C++ 2015, 2017, 2019 or 2022
+You can build Panda3D with the Microsoft Visual C++ 2017, 2019 or 2022
 compiler, which can be downloaded for free from the [Visual Studio site](https://visualstudio.microsoft.com/downloads/).
 You will also need to install the [Windows SDK](https://developer.microsoft.com/en-us/windows/downloads/windows-sdk),
 and if you intend to target Windows Vista, you will also need the

doc/CODING_STYLE.md

@@ -184,7 +184,7 @@ Try to group logically-similar lines, separating them with a single blank line.
 Modern language features
 ------------------------
 
-Panda3D is a C++11 project.  The use of the following modern language features
+Panda3D is a C++14 project.  The use of the following modern language features
 is greatly encouraged:
 
 1. `nullptr` over `NULL`
@@ -197,4 +197,4 @@ creating a typedef for the container type instead.
 Avoid using `std::function` in cases where a lambda can be accepted directly
 (using a template function), since it has extra overhead over lambdas.
 
-C++14 and C++17 features should be avoided for now.
+C++17 features should be avoided for now.

dtool/CompilerFlags.cmake

@@ -51,8 +51,8 @@ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GCC")
 
 endif()
 
-# Panda3D is now a C++11 project.
-set(CMAKE_CXX_STANDARD 11)
+# Panda3D is now a C++14 project.
+set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 # Set certain CMake flags we expect

dtool/src/dtoolbase/dtoolbase_cc.h

@@ -110,9 +110,9 @@ typedef std::ios::seekdir ios_seekdir;
 #define INLINE inline
 #endif
 
-// Determine the availability of C++11 features.
-#if defined(_MSC_VER) && _MSC_VER < 1900 // Visual Studio 2015
-#error Microsoft Visual C++ 2015 or later is required to compile Panda3D.
+// Determine the availability of C++14 features.
+#if defined(_MSC_VER) && _MSC_VER < 1910 // Visual Studio 2017
+#error Microsoft Visual C++ 2017 or later is required to compile Panda3D.
 #endif
 
 // This is just to support code generated with older versions of interrogate.

makepanda/makepanda.py

@@ -156,7 +156,7 @@ def usage(problem):
     print("  --everything      (enable every third-party lib)")
     print("  --directx-sdk=X   (specify version of DirectX SDK to use: jun2010, aug2009)")
     print("  --windows-sdk=X   (specify Windows SDK version, eg. 7.1, 8.1, 10 or 11.  Default is 8.1)")
-    print("  --msvc-version=X  (specify Visual C++ version, eg. 10, 11, 12, 14, 14.1, 14.2, 14.3.  Default is 14)")
+    print("  --msvc-version=X  (specify Visual C++ version, eg. 14.1, 14.2, 14.3.  Default is 14.1)")
     print("  --use-icl         (experimental setting to use an intel compiler instead of MSVC on Windows)")
     print("")
     print("The simplest way to compile panda is to just type:")
@@ -309,8 +309,8 @@ def parseopts(args):
 
     if GetTarget() == 'windows':
         if not MSVC_VERSION:
-            print("No MSVC version specified. Defaulting to 14 (Visual Studio 2015).")
-            MSVC_VERSION = (14, 0)
+            print("No MSVC version specified. Defaulting to 14.1 (Visual Studio 2017).")
+            MSVC_VERSION = (14, 1)
         else:
             try:
                 MSVC_VERSION = tuple(int(d) for d in MSVC_VERSION.split('.'))[:2]
@@ -319,12 +319,10 @@ def parseopts(args):
             except:
                 usage("Invalid setting for --msvc-version")
 
-        if MSVC_VERSION < (14, 0):
+        if MSVC_VERSION < (14, 1):
             warn_prefix = "%sERROR:%s " % (GetColor("red"), GetColor())
             print("=========================================================================")
-            print(warn_prefix + "Support for MSVC versions before 2015 has been discontinued.")
-            print(warn_prefix + "For more information, or any questions, please visit:")
-            print(warn_prefix + "  https://github.com/panda3d/panda3d/issues/288")
+            print(warn_prefix + "Support for MSVC versions before 2017 has been discontinued.")
             print("=========================================================================")
             sys.stdout.flush()
             time.sleep(1.0)
@@ -1313,7 +1311,7 @@ def CompileCxx(obj,src,opts):
 
     if (COMPILER=="GCC"):
         if (src.endswith(".c")): cmd = GetCC() +' -fPIC -c -o ' + obj
-        else:                    cmd = GetCXX()+' -std=gnu++11 -ftemplate-depth-70 -fPIC -c -o ' + obj
+        else:                    cmd = GetCXX()+' -std=gnu++14 -ftemplate-depth-70 -fPIC -c -o ' + obj
         for (opt, dir) in INCDIRECTORIES:
             if (opt=="ALWAYS") or (opt in opts): cmd += ' -I' + BracketNameWithQuotes(dir)
         for (opt, dir) in FRAMEWORKDIRECTORIES: