From 8bedd52e2b15666e53c90c97a04e70622f25783e Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Wed, 1 Apr 2020 16:32:21 +0100
Subject: [PATCH] HID: allow raw-descriptor parsing in the XML

Also fix deadband computation (do it after min-max ranging)
---
 src/Input/FGEventInput.cxx    |  6 ++---
 src/Input/FGHIDEventInput.cxx | 45 +++++++++++++++++++++++++----------
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/src/Input/FGEventInput.cxx b/src/Input/FGEventInput.cxx
index 4b0a17aea..08c455f0b 100644
--- a/src/Input/FGEventInput.cxx
+++ b/src/Input/FGEventInput.cxx
@@ -176,12 +176,12 @@ void FGAxisEvent::fire( FGEventData & eventData )
   // We need a copy of the  FGEventData struct to set the new value and to avoid side effects
   FGEventData ed = eventData;
 
-  if( fabs(ed.value) < deadband )
-    ed.value = 0.0;
-
   if( minRange != maxRange )
     ed.value = 2.0*(eventData.value-minRange)/(maxRange-minRange)-1.0;
 
+  if( fabs(ed.value) < deadband )
+    ed.value = 0.0;
+    
   if (interpolater) {
     if ((ed.value < 0.0) && mirrorInterpolater) {
       // mirror the positive interpolation for negative values
diff --git a/src/Input/FGHIDEventInput.cxx b/src/Input/FGHIDEventInput.cxx
index 4422a73ea..65f50a631 100644
--- a/src/Input/FGHIDEventInput.cxx
+++ b/src/Input/FGHIDEventInput.cxx
@@ -318,6 +318,9 @@ private:
     /// is inaccessible, or devices with broken descriptors
     bool _haveLocalDescriptor = false;
     
+    /// allow specifying the descriptor as hex bytes in XML
+    std::vector<uint8_t>_rawXMLDescriptor;
+    
     // all sets which will be send on the next update() call.
     std::set<Report*> _dirtyReports;
 };
@@ -384,6 +387,13 @@ void FGHIDDevice::Configure(SGPropertyNode_ptr node)
             defineReport(report);
         }
     }
+    
+    if (node->hasChild("hid-raw-descriptor")) {
+        _rawXMLDescriptor = simgear::strutils::decodeHex(node->getStringValue("hid-raw-descriptor"));
+        if (debugEvents) {
+            SG_LOG(SG_INPUT, SG_INFO, GetUniqueName() << " will configure using XML-defined raw HID descriptor");
+        }
+    }
 }
 
 bool FGHIDDevice::Open()
@@ -395,6 +405,19 @@ bool FGHIDDevice::Open()
         return false;
     }
 
+#if !defined(SG_WINDOWS)
+    if (_rawXMLDescriptor.empty()) {
+        _rawXMLDescriptor.resize(2048);
+        int descriptorSize = hid_get_descriptor(_device, _rawXMLDescriptor.data(), _rawXMLDescriptor.size());
+        if (descriptorSize <= 0) {
+           SG_LOG(SG_INPUT, SG_WARN, "HID: " << GetUniqueName() << " failed to read HID descriptor");
+           return false;
+        }
+        
+        _rawXMLDescriptor.resize(descriptorSize);
+    }
+#endif
+    
     if (!_haveLocalDescriptor) {
         bool ok = parseUSBHIDDescriptor();
         if (!ok)
@@ -422,26 +445,22 @@ bool FGHIDDevice::Open()
 bool FGHIDDevice::parseUSBHIDDescriptor()
 {
 #if defined(SG_WINDOWS)
-    SG_LOG(SG_INPUT, SG_ALERT, GetUniqueName() << ": on Windows, there is no way to extract the UDB-HID report descriptor. "
-           << "\nPlease supply the report descriptor in the device XML configuration.");
-    return false;
-#endif
-    
-    unsigned char reportDescriptor[1024];
-    int descriptorSize = hid_get_descriptor(_device, reportDescriptor, 1024);
-    if (descriptorSize <= 0) {
-        SG_LOG(SG_INPUT, SG_WARN, "HID: " << GetUniqueName() << " failed to read HID descriptor");
+    if (_rawXMLDescriptor.empty()) {
+        SG_LOG(SG_INPUT, SG_ALERT, GetUniqueName() << ": on Windows, there is no way to extract the UDB-HID report descriptor. "
+               << "\nPlease supply the report descriptor in the device XML configuration.");
+        SG_LOG(SG_INPUT, SG_ALERT, "See this page:<> for information on extracting the report descriptor on Windows");
         return false;
     }
+#endif
     
     if (debugEvents) {
         SG_LOG(SG_INPUT, SG_INFO, "\nHID: descriptor for:" << GetUniqueName());
         {
             std::ostringstream byteString;
             
-            for (int i=0; i<descriptorSize; ++i) {
-                byteString << hexTable[reportDescriptor[i] >> 4];
-                byteString << hexTable[reportDescriptor[i] & 0x0f];
+            for (auto i=0; i<_rawXMLDescriptor.size(); ++i) {
+                byteString << hexTable[_rawXMLDescriptor[i] >> 4];
+                byteString << hexTable[_rawXMLDescriptor[i] & 0x0f];
                 byteString << " ";
             }
             SG_LOG(SG_INPUT, SG_INFO, "\tbytes: " << byteString.str());
@@ -449,7 +468,7 @@ bool FGHIDDevice::parseUSBHIDDescriptor()
     }
     
     hid_item* rootItem = nullptr;
-    hid_parse_reportdesc(reportDescriptor, descriptorSize, &rootItem);
+    hid_parse_reportdesc(_rawXMLDescriptor.data(), _rawXMLDescriptor.size(), &rootItem);
     if (debugEvents) {
         SG_LOG(SG_INPUT, SG_INFO, "\nHID: scan for:" << GetUniqueName());
     }