Add details on how to fix unpatched web client and 'windows SDK not found'

misc/compile-fixes.md

@@ -0,0 +1,99 @@
+Visual studio unsupported platform toolset
+---------------------
+To fix the ```Error MSB8036 The Windows SDK version 5.1 was not found. Install the required version of Windows SDK or change the SDK version in the project property pages or by right-clicking the solution and selecting "Retarget solution"```
+* Right click **ClassiCube** project (it's under the *Solution 'ClassiCube'* in the *Solution Explorer* pane)
+* Click **Properties**
+* Make sure you are in **General** tab under **Configuration Properties**
+* You should see a dropdown named **Platform Toolset**. Click on it.
+* Change it to one of the toolsets in the list that pops up.
+* Click **OK**. You should be able to compile now
+
+![image](https://user-images.githubusercontent.com/6509348/60266950-727e4780-992c-11e9-98fb-85eb34959e93.png)
+
+Common compilation errors
+---------------------
+#### Undefined reference to 'clock_gettime'
+Add ```-lrt``` when compiling. Occurs when using glibc versions before 2.17.
+
+#### fatal error: execinfo.h: No such file or directory
+Install ```libexecinfo``` package. Occurs when using musl.
+
+#### Undefined reference to 'backtrace'
+Add ```-lexecinfo``` when compiling. Occurs when using musl.
+  
+#### Undefined reference to 'getcontext'
+Occurs when using musl. Change
+```C
+getcontext(&ctx);
+Logger_AbortCommon(result, raw_msg, &ctx);
+```
+to
+```C
+Logger_AbortCommon(result, raw_msg, NULL);
+```
+
+Webclient patches
+---------------------
+#### Starting game **Error 00000002 when setting current directory**
+This is caused by IndexedDB not being initialised, which also means saved maps are lost when the tab is closed.
+
+Due to how IndexedDB works, you must load and initialise it before the game starts. Change:
+
+```
+    <script type='text/javascript'>
+      var Module = {
+        preRun: [],
+...
+```
+to
+```
+    <script type='text/javascript'>
+      // need to load IndexedDB before running the game
+      function preloadIndexedDB() {
+        addRunDependency('load-idb');
+        FS.mkdir('/classicube');
+        FS.mount(IDBFS, {}, '/classicube');
+        FS.syncfs(true, function(err) { 
+            assert(!err); 
+            removeRunDependency('load-idb');
+        })
+      }
+
+      var Module = {
+        preRun: [ preloadIndexedDB ],
+...
+```
+
+#### Mouse scrolling not properly prevented
+With recent chrome/firefox versions, page is still scrolled and console is spammed with\
+```"[Intervention] Unable to preventDefault inside passive event listener due to target being treated as passive."```
+
+You need to to register events as a passive handler. Look for something like:
+```
+eventHandler.target.addEventListener(eventHandler.eventTypeString, jsEventHandler, eventHandler.useCapture);
+```
+and change to 
+```
+eventHandler.target.addEventListener(eventHandler.eventTypeString, jsEventHandler, { useCapture: eventHandler.useCapture, passive: false });
+```
+
+#### Texture pack confirm dialog always shows *Download size: Determining*..
+Unfortunately emscripten doesn't store content-length for HEAD http requests. This can be fixed.
+
+First you need to find at what offset emscripten stores content-length. Look for something like:
+```
+xhr.onprogress = function(e) {
+...
+      Fetch.setu64(fetch + 32, e.total);
+```
+then look for
+```
+xhr.onload = function(e) {
+...
+```
+and finally change that to
+```
+xhr.onload = function(e) { 
+    Fetch.setu64(fetch + 32, e.total);
+...
+```