1 files changed, 66 insertions, 0 deletions
diff --git a/librsvg-c/src/dpi.rs b/librsvg-c/src/dpi.rs
new file mode 100644
index 00000000..b2e15eef
--- /dev/null
+++ b/librsvg-c/src/dpi.rs
@@ -0,0 +1,66 @@
+//! Legacy C API for setting a default DPI (dots per inch = DPI).
+//!
+//! There are two deprecated functions, `rsvg_set_default_dpi` and
+//! `rsvg_set_default_dpi_x_y`, which set global values for the default DPI to be used
+//! with `RsvgHandle`.  In turn, `RsvgHandle` assumes that when its own DPI value is set
+//! to `0.0` (which is in fact its default), it will fall back to the global DPI.
+//!
+//! This is clearly not thread-safe, but it is the legacy behavior.
+//!
+//! This module encapsulates that behavior so that the `rsvg_internals` crate
+//! can always have immutable DPI values as intended.
+
+// This is configurable at runtime
+const DEFAULT_DPI_X: f64 = 90.0;
+const DEFAULT_DPI_Y: f64 = 90.0;
+
+static mut DPI_X: f64 = DEFAULT_DPI_X;
+static mut DPI_Y: f64 = DEFAULT_DPI_Y;
+
+#[derive(Debug, Copy, Clone, Default)]
+pub(crate) struct Dpi {
+    x: f64,
+    y: f64,
+}
+
+impl Dpi {
+    pub(crate) fn new(x: f64, y: f64) -> Dpi {
+        Dpi { x, y }
+    }
+
+    pub(crate) fn x(&self) -> f64 {
+        if self.x <= 0.0 {
+            unsafe { DPI_X }
+        } else {
+            self.x
+        }
+    }
+
+    pub(crate) fn y(&self) -> f64 {
+        if self.y <= 0.0 {
+            unsafe { DPI_Y }
+        } else {
+            self.y
+        }
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn rsvg_set_default_dpi_x_y(dpi_x: libc::c_double, dpi_y: libc::c_double) {
+    if dpi_x <= 0.0 {
+        DPI_X = DEFAULT_DPI_X;
+    } else {
+        DPI_X = dpi_x;
+    }
+
+    if dpi_y <= 0.0 {
+        DPI_Y = DEFAULT_DPI_Y;
+    } else {
+        DPI_Y = dpi_y;
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn rsvg_set_default_dpi(dpi: libc::c_double) {
+    rsvg_set_default_dpi_x_y(dpi, dpi);
+}