Fix build_distrib.py script for Python 2.7 and Python 3.4 (latest pip

versions are broken with these old Pythons).

Fix screenshot.py example sometimes failing.

When compiling for Python 3.4 you can encounter the the missing
"ammintrin.h" header file error. Just copy it from the VS 2019
include/ directory.

For Pythons 3.5 / 3.6 / 3.7 / 3.8 / 3.9 you can use the same VC++ 14.2
(VS 2019) compiler which is binary compatible with VC++ 14.1 (VS 2017)
and VC++ 14.0 (VS 2015).

Currently the subprocess.exe executable built by Python 3.4 (VC++ 10.0
compiler) gives the least amount of false-positives by AVs on
virustotal.com . For comparison: Py34 (1/69), Py27 (2/69),
Py39 (5/69). Results differ for 32bit and 64bit binaries.

Author: cztomczak

examples/screenshot.py

@@ -158,6 +158,8 @@ def save_screenshot(browser):
                             "raw", "RGBA", 0, 1)
     image.save(SCREENSHOT_PATH, "PNG")
     print("[screenshot.py] Saved image: {path}".format(path=SCREENSHOT_PATH))
+    # See comments in exit_app() why PostTask must be used
+    cef.PostTask(cef.TID_UI, exit_app, browser)
 
 
 def open_with_default_application(path):
@@ -188,9 +190,10 @@ def OnLoadingStateChange(self, browser, is_loading, **_):
             # Loading is complete
             sys.stdout.write(os.linesep)
             print("[screenshot.py] Web page loading is complete")
-            save_screenshot(browser)
-            # See comments in exit_app() why PostTask must be used
-            cef.PostTask(cef.TID_UI, exit_app, browser)
+            print("[screenshot.py] Will save screenshot in 2 seconds")
+            # Give up to 2 seconds for the OnPaint call. Most of the time
+            # it is already called, but sometimes it may be called later.
+            cef.PostDelayedTask(cef.TID_UI, 2000, save_screenshot, browser)
 
     def OnLoadError(self, browser, frame, error_code, failed_url, **_):
         """Called when the resource load for a navigation fails

tools/build_distrib.py

@@ -353,8 +353,14 @@ def install_upgrade_requirements(pythons):
               " for: {name}".format(name=python["name"]))
 
         # Upgrade pip
-        command = ("\"{python}\" -m pip install --upgrade pip"
-                   .format(python=python["executable"]))
+        pip_version = "pip"
+        # Old Python versions require specific versions of pip, latest versions are broken with these.
+        if python["version2"] == (2, 7):
+            pip_version = "pip==20.3.4"
+        elif python["version2"] == (3, 4):
+            pip_version = "pip==19.1.1"
+        command = ("\"{python}\" -m pip install --upgrade {pip_version}"
+                   .format(python=python["executable"], pip_version=pip_version))
         command = sudo_command(command, python=python["executable"])
         pcode = subprocess.call(command, shell=True)
         if pcode != 0:
@@ -522,39 +528,37 @@ def build_cefpython_modules(pythons, arch):
 
 
 def backup_subprocess_executable_issue342(python):
-    """Use subprocess executable build by Python 2.7 to avoid
-    false-positives by AVs when building subprocess with Python 3.
-    Windows-only issue."""
+    """Use subprocess executable built by Python 3.4 to have the least amount of
+    false-positives by AVs. Windows-only issue."""
     if not WINDOWS:
         return
     if python["version2"] == (2, 7):
         print("[build_distrib.py] Backup subprocess executable built"
-              " with Python 2.7 (Issue #342)")
+              " with Python 3.4 (Issue #342)")
         cefpython_binary_basename = get_cefpython_binary_basename(
                 get_os_postfix2_for_arch(python["arch"]))
         cefpython_binary = os.path.join(BUILD_DIR, cefpython_binary_basename)
         assert os.path.isdir(cefpython_binary)
         src = os.path.join(cefpython_binary, "subprocess.exe")
         dst = os.path.join(BUILD_CEFPYTHON,
-                           "subprocess_py27_{arch}_issue342.exe"
+                           "subprocess_py34_{arch}_issue342.exe"
                            .format(arch=python["arch"]))
         shutil.copy(src, dst)
 
 
 def restore_subprocess_executable_issue342(arch):
-    """Use subprocess executable build by Python 2.7 to avoid
-    false-positives by AVs when building subprocess with Python 3.
-    Windows-only issue."""
+    """Use subprocess executable built by Python 3.4 to have the least amount of
+    false-positives by AVs. Windows-only issue."""
     if not WINDOWS:
         return
     print("[build_distrib.py] Restore subprocess executable built"
-          " with Python 2.7 (Issue #342)")
+          " with Python 3.4 (Issue #342)")
     cefpython_binary_basename = get_cefpython_binary_basename(
             get_os_postfix2_for_arch(arch))
     cefpython_binary = os.path.join(BUILD_DIR, cefpython_binary_basename)
     assert os.path.isdir(cefpython_binary)
     src = os.path.join(BUILD_CEFPYTHON,
-                       "subprocess_py27_{arch}_issue342.exe"
+                       "subprocess_py34_{arch}_issue342.exe"
                        .format(arch=arch))
     assert os.path.isfile(src)
     dst = os.path.join(cefpython_binary, "subprocess.exe")