Feature: opt-in survey when exiting a game

On first start-up, the game will ask if you want to participate
in our automated survey. You have to opt-in, and can easily opt-out
(via the Options) at any time.

When opt-in, whenever you exit a game, a JSON blob will be send
to the survey server hosted by OpenTTD. This JSON blob contains
information that gives a global picture of the game just played:
- What settings were used
- How many humans vs AIs
- How long the game has been played
- Basic information about the OS / CPU

All this information is kept very generic, so there is no
chance we send private information to our survey server.
Nothing in the JSON blob could identify you as a person; it
mostly tells about the game played. At any time you can see
what the JSON blob includes, by pressing the "Preview Survey
Results" button in-game.

src/widgets/ai_widget.h

@@ -29,7 +29,7 @@ enum AIConfigWidgets {
 	WID_AIC_CONFIGURE,        ///< Change AI settings button.
 	WID_AIC_CLOSE,            ///< Close window button.
 	WID_AIC_TEXTFILE,         ///< Open AI readme, changelog (+1) or license (+2).
-	WID_AIC_CONTENT_DOWNLOAD = WID_AIC_TEXTFILE + TFT_END, ///< Download content button.
+	WID_AIC_CONTENT_DOWNLOAD = WID_AIC_TEXTFILE + TFT_CONTENT_END, ///< Download content button.
 };
 
 #endif /* WIDGETS_AI_WIDGET_H */

src/widgets/game_widget.h

@@ -20,7 +20,7 @@ enum GSConfigWidgets {
 	WID_GSC_SCROLLBAR,        ///< Scrollbar to scroll through the selected AIs.
 	WID_GSC_CHANGE,           ///< Select another Game Script button.
 	WID_GSC_TEXTFILE,         ///< Open GS readme, changelog (+1) or license (+2).
-	WID_GSC_CONTENT_DOWNLOAD = WID_GSC_TEXTFILE + TFT_END, ///< Download content button.
+	WID_GSC_CONTENT_DOWNLOAD = WID_GSC_TEXTFILE + TFT_CONTENT_END, ///< Download content button.
 	WID_GSC_ACCEPT,           ///< Accept ("Close") button
 	WID_GSC_RESET,            ///< Reset button.
 };

src/widgets/network_content_widget.h

@@ -36,7 +36,7 @@ enum NetworkContentListWidgets {
 	WID_NCL_DETAILS,        ///< Panel with content details.
 	WID_NCL_TEXTFILE,       ///< Open readme, changelog (+1) or license (+2) of a file in the content window.
 
-	WID_NCL_SELECT_ALL = WID_NCL_TEXTFILE + TFT_END, ///< 'Select all' button.
+	WID_NCL_SELECT_ALL = WID_NCL_TEXTFILE + TFT_CONTENT_END, ///< 'Select all' button.
 	WID_NCL_SELECT_UPDATE,  ///< 'Select updates' button.
 	WID_NCL_UNSELECT,       ///< 'Unselect all' button.
 	WID_NCL_OPEN_URL,       ///< 'Open url' button.

src/widgets/network_widget.h

@@ -119,4 +119,14 @@ enum NetworkAskRelayWidgets {
 	WID_NAR_YES_ALWAYS, ///< "Yes, always" button.
 };
 
+/** Widgets of the #NetworkAskSurveyWindow class. */
+enum NetworkAskSurveyWidgets {
+	WID_NAS_CAPTION,    ///< Caption of the window.
+	WID_NAS_TEXT,       ///< Text in the window.
+	WID_NAS_PREVIEW,    ///< "Preview" button.
+	WID_NAS_LINK,       ///< "Details & Privacy" button.
+	WID_NAS_NO,         ///< "No" button.
+	WID_NAS_YES,        ///< "Yes" button.
+};
+
 #endif /* WIDGETS_NETWORK_WIDGET_H */

src/widgets/newgrf_widget.h

@@ -47,7 +47,7 @@ enum NewGRFStateWidgets {
 	WID_NS_NEWGRF_INFO,       ///< Panel for Info on selected NewGRF.
 	WID_NS_OPEN_URL,          ///< Open URL of NewGRF.
 	WID_NS_NEWGRF_TEXTFILE,   ///< Open NewGRF readme, changelog (+1) or license (+2).
-	WID_NS_SET_PARAMETERS = WID_NS_NEWGRF_TEXTFILE + TFT_END,   ///< Open Parameters Window for selected NewGRF for editing parameters.
+	WID_NS_SET_PARAMETERS = WID_NS_NEWGRF_TEXTFILE + TFT_CONTENT_END,   ///< Open Parameters Window for selected NewGRF for editing parameters.
 	WID_NS_VIEW_PARAMETERS,   ///< Open Parameters Window for selected NewGRF for viewing parameters.
 	WID_NS_TOGGLE_PALETTE,    ///< Toggle Palette of selected, active NewGRF.
 	WID_NS_APPLY_CHANGES,     ///< Apply changes to NewGRF config.

src/widgets/settings_widget.h

@@ -28,23 +28,27 @@ enum GameOptionsWidgets {
 	WID_GO_BASE_GRF_DROPDOWN,      ///< Use to select a base GRF.
 	WID_GO_BASE_GRF_STATUS,        ///< Info about missing files etc.
 	WID_GO_BASE_GRF_TEXTFILE,      ///< Open base GRF readme, changelog (+1) or license (+2).
-	WID_GO_BASE_GRF_DESCRIPTION = WID_GO_BASE_GRF_TEXTFILE + TFT_END,     ///< Description of selected base GRF.
+	WID_GO_BASE_GRF_DESCRIPTION = WID_GO_BASE_GRF_TEXTFILE + TFT_CONTENT_END,     ///< Description of selected base GRF.
 	WID_GO_BASE_SFX_DROPDOWN,      ///< Use to select a base SFX.
 	WID_GO_TEXT_SFX_VOLUME,        ///< Sound effects volume label.
 	WID_GO_BASE_SFX_VOLUME,        ///< Change sound effects volume.
 	WID_GO_BASE_SFX_TEXTFILE,      ///< Open base SFX readme, changelog (+1) or license (+2).
-	WID_GO_BASE_SFX_DESCRIPTION = WID_GO_BASE_SFX_TEXTFILE + TFT_END,     ///< Description of selected base SFX.
+	WID_GO_BASE_SFX_DESCRIPTION = WID_GO_BASE_SFX_TEXTFILE + TFT_CONTENT_END,     ///< Description of selected base SFX.
 	WID_GO_BASE_MUSIC_DROPDOWN,    ///< Use to select a base music set.
 	WID_GO_TEXT_MUSIC_VOLUME,      ///< Music volume label.
 	WID_GO_BASE_MUSIC_VOLUME,      ///< Change music volume.
 	WID_GO_BASE_MUSIC_JUKEBOX,     ///< Open the jukebox.
 	WID_GO_BASE_MUSIC_STATUS,      ///< Info about corrupted files etc.
 	WID_GO_BASE_MUSIC_TEXTFILE,    ///< Open base music readme, changelog (+1) or license (+2).
-	WID_GO_BASE_MUSIC_DESCRIPTION = WID_GO_BASE_MUSIC_TEXTFILE + TFT_END, ///< Description of selected base music set.
+	WID_GO_BASE_MUSIC_DESCRIPTION = WID_GO_BASE_MUSIC_TEXTFILE + TFT_CONTENT_END, ///< Description of selected base music set.
 	WID_GO_VIDEO_ACCEL_BUTTON,     ///< Toggle for video acceleration.
 	WID_GO_VIDEO_VSYNC_BUTTON,     ///< Toggle for video vsync.
 	WID_GO_REFRESH_RATE_DROPDOWN,  ///< Dropdown for all available refresh rates.
 	WID_GO_VIDEO_DRIVER_INFO,      ///< Label showing details about the current video driver.
+	WID_GO_SURVEY_SEL,             ///< Selection to hide survey if no JSON library is compiled in.
+	WID_GO_SURVEY_PARTICIPATE_BUTTON, ///< Toggle for participating in the automated survey.
+	WID_GO_SURVEY_LINK_BUTTON,     ///< Button to open browser to go to the survey website.
+	WID_GO_SURVEY_PREVIEW_BUTTON,  ///< Button to open a preview window with the survey results
 };
 
 /** Widgets of the #GameSettingsWindow class. */