gamnit: implement `camera_control` for linux

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/gamnit/camera_control_linux.nit b/lib/gamnit/camera_control_linux.nit
new file mode 100644 (file)
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+++ b/lib/gamnit/camera_control_linux.nit
@@ -0,0 +1,64 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Mouse wheel and middle mouse button to control camera
+module camera_control_linux
+
+import linux
+import camera_control
+
+redef class EulerCamera
+
+       # Zoom factor, default at 1.2, higher means more reactive zoom effect
+       var camera_zoom_mod = 1.2 is writable
+
+       # Scoll trigger button mask from SDL2 (1: left, 2: middle, 4: right)
+       #
+       # Set to 0 to deactivate the scrolling feature.
+       var camera_pan_mask = 2 is writable
+
+       redef fun accept_scroll_and_zoom(event)
+       do
+               # Zoom
+               if event isa GamnitMouseWheelEvent then
+                       var dy = event.y
+                       var mod = camera_zoom_mod
+                       if dy > 0.0 then
+                               # Zoom in when moving the wheel up
+                               mod = 1.0/mod
+                       else dy = -dy
+
+                       position.z *= dy * mod
+                       return true
+               end
+
+               # Scroll
+               var but_mask = camera_pan_mask
+               if but_mask != 0 and event isa GamnitPointerEvent then
+                       var native = event.native
+                       if native isa SDLMouseMotionEvent and native.state & but_mask == but_mask then
+                               var dx = native.xrel.to_f
+                               var dy = native.yrel.to_f
+
+                               var world_height = field_of_view_y.sin * position.z
+                               var mod = app.display.as(not null).height.to_f / world_height
+                               position.x -= dx / mod
+                               position.y += dy / mod # Y is inverted between the input and output
+                               return true
+                       end
+               end
+
+               return false
+       end
+end