Changes between Version 1 and Version 2 of MapGuideRfc170

Timestamp:

Apr 24, 2019, 6:17:19 PM (5 years ago)

Author:

jng

Comment:

--

MapGuideRfc170

@@ -53 +53 @@
 In the Fusion viewer, if it is known that the XYZ tile provider is being used in the CREATERUNTIMEMAP response, it will create an OpenLayers.Layer.XYZ instance to read such tiles instead of the tiled version of OpenLayers.Layer.MapGuide
 
+=== Configurable TileExtentOffset ===
+
+In addition to meta-tiling parameters, the (previously-global) {{{TileExtentOffset}}} server configuration property is now available as a tileset-specific parameter.
+
 === Meta-tiling ===
 
@@ -59 +63 @@
 However, this implementation has not yet been integrated back into trunk so as a result, it has not surfaced as a feature in any release of MapGuide since the RFC was implemented.
 
-For this RFC, we will take the RFC90 implementation of meta-tiling and retro-fit it into the Tile Set Definition infrastructure.
-
-Meta-tiling support will be surfaced via new tile set parameters:
+For this RFC, we will take the RFC90 implementation of meta-tiling and retro-fit it into the new Tile Set Definition infrastructure.
+
+Firstly, we will add new {{{RenderTile}}} and {{{RenderTileXYZ}}} primitives that accept a meta-tiling factor:
+
+{{{
+class MG_MAPGUIDE_API MgRenderingService : public MgService
+{
+...
+EXTERNAL_API:
+    /////////////////////////////////////////////////////////////////
+    /// \brief
+    /// Returns the specified base map tile for the given map.
+    ///
+    /// \remarks
+    /// This method only renders the given tile. No tile caching is performed
+    /// by this method. To render and cache the tile, use the 
+    /// \link MgTileService::GetTile GetTile \endlink method instead. However,
+    /// using that method will use default tile width/height/dpi/format specified
+    /// in your MapGuide Server configuration
+    ///
+    /// \param map
+    /// Input
+    /// map object containing current state of map.
+    /// \param baseMapLayerGroupName
+    /// Input
+    /// Specifies the name of the baseMapLayerGroup for which to render the tile.
+    /// \param tileColumn
+    /// Input
+    /// Specifies the column index of the tile to return.
+    /// \param tileRow
+    /// Input
+    /// Specifies the row index of the tile to return.
+    /// \param tileWidth
+    /// Input
+    /// Specifies the width of the tile to return.
+    /// \param tileHeight
+    /// Input
+    /// Specifies the height of the tile to return.
+    /// \param tileDpi
+    /// Input
+    /// Specifies the dpi the tile to return.
+    /// \param tileImageFormat
+    /// Input
+    /// Specifies the image format of the tile. See \link MgImageFormats \endlink
+    /// \param tileExtentOffset
+    /// Specifies the ratio by which the tile to be rendered should be "buffered out". The tile will be rendered at the specified width
+    /// multiplied by the given ratio, which will be cropped back to the original requested size after rendering. This is to improve
+    /// label placement on rendered tiles by giving extra "breathing space" to label placement algorithms.
+    /// \param metaTilingFactor
+    /// The meta-tiling factor, If less than or equal to 1 no meta-tiling is done. If greater than 1, a tile m times the original requested
+    /// size is rendered instead (where m is the specified factor)
+    ///
+    /// \return
+    /// A byte reader containing the rendered tile image. If metaTilingFactor is greater than 1, then a raw image frame buffer is returned 
+    /// instead. This raw image frame buffer is not intended to be used by MapGuide applications and is reserved for the rendering infrastructre
+    /// to sub-divide back into tiles of the original requested size.
+    ///
+    /// \since 3.3
+    virtual MgByteReader* RenderTile(
+        MgMap* map,
+        CREFSTRING baseMapLayerGroupName,
+        INT32 tileColumn,
+        INT32 tileRow,
+        INT32 tileWidth,
+        INT32 tileHeight,
+        INT32 tileDpi,
+        CREFSTRING tileImageFormat,
+        double tileExtentOffset,
+        INT32 metaTileFactor) = 0;
+
+    /////////////////////////////////////////////////////////////////
+    /// \brief
+    /// Returns the specified map tile for the given map. Tile structure is
+    /// based on the XYZ tiling scheme used by Google Maps, OpenStreetMap, and
+    /// others
+    ///
+    /// \param map
+    /// Input
+    /// map object containing current state of map.
+    /// \param baseMapLayerGroupName
+    /// Input
+    /// Specifies the name of the baseMapLayerGroup for which to render the tile.
+    /// \param x
+    /// Input
+    /// Specifies the row index of the tile to return.
+    /// \param y
+    /// Input
+    /// Specifies the column index of the tile to return.
+    /// \param z
+    /// Input
+    /// Specifies the zoom level of the tile to return.
+    /// \param dpi
+    /// Input
+    /// Specifies the dpi of the tile to return.
+    /// \param tileImageFormat
+    /// Input
+    /// Specifies the image format of the tile to return.
+    /// \param tileExtentOffset
+    /// Specifies the ratio by which the tile to be rendered should be "buffered out". The tile will be rendered at the specified width
+    /// multiplied by the given ratio, which will be cropped back to the original requested size after rendering. This is to improve
+    /// label placement on rendered tiles by giving extra "breathing space" to label placement algorithms.
+    /// \param metaTilingFactor
+    /// The meta-tiling factor, If less than or equal to 1 no meta-tiling is done. If greater than 1, a tile m times the original requested
+    /// size is rendered instead (where m is the specified factor)
+    ///
+    /// \return
+    /// A byte reader containing the rendered tile image. If metaTilingFactor is greater than 1, then a raw image frame buffer is returned 
+    /// instead. This raw image frame buffer is not intended to be used by MapGuide applications and is reserved for the rendering infrastructre
+    /// to sub-divide back into tiles of the original requested size.
+    ///
+    /// \since 3.3
+    virtual MgByteReader* RenderTileXYZ(
+        MgMap* map,
+        CREFSTRING baseMapLayerGroupName,
+        INT32 x,
+        INT32 y,
+        INT32 z,
+        INT32 dpi,
+        CREFSTRING tileImageFormat,
+        double tileExtentOffset,
+        INT32 metaTilingFactor) = 0;
+};
+}}}
+
+These new overloads are designated {{{EXTERNAL_API}}} because meta-tiles are not intended to be consumed by regular MapGuide applications. They are raw image frame buffers that the rendering infrastructure will use to sub-divide back into tiles of the original requested size. But at the same time, these overloads have to be present in the {{{MgRenderingService}}} contract to allow a server-based tile service to still request meta-tiles through a proxy instance (should a server-based instance not be available) hence the {{{EXTERNAL_API}}} designation.
+
+Meta-tiling support will be surfaced via new tile set definition parameters:
 
  * {{{MetaTileFactor}}}
  * {{{LockMethod}}}
 
+Meta-tiling has no effect for tile formats that are not image-based (eg. UTFGrid)
+
 === HTTP caching headers ===
 
-=== Configurable TileExtentOffset ===
-
-In addition to meta-tiling parameters, the (previously-global) {{{TileExtentOffset}}} server configuration property is now available as a tileset-specific parameter.
-
 == Implications ==
 
+Tiles generated through meta-tiling may have subtle differences in label placement due to being "cut" from a parent tile that is {{{x}}} times bigger (where {{{x}}} = meta-tiling factor), thus affording the tile renderer more "breathing space" in determining optimal label placement for applicable features that a regular tile would not have.
+
 == Test Plan ==
 
+Add unit tests to render meta-tiles and also render baseline regular tiles for comparison. With the exception of subtle differences in label placement, verify that the tiles cut from meta-tiles are visually the same as regular tiles (esp. Line/Polygon features)
+
 == Funding / Resources ==