add knob widget

src/nuklear_knob.c

@@ -0,0 +1,250 @@
+#include "nuklear.h"
+#include "nuklear_internal.h"
+
+/* ===============================================================
+ *
+ *                               KNOB
+ *
+ * ===============================================================*/
+
+NK_LIB float
+nk_knob_behavior(nk_flags *state, struct nk_input *in,
+    struct nk_rect bounds, float knob_min, float knob_max, float knob_value,
+    float knob_step, float knob_steps,
+    enum nk_heading zero_direction, float dead_zone_percent)
+{
+    struct nk_vec2 origin;
+    float angle = 0.0f;
+    origin.x = bounds.x + (bounds.w / 2);
+    origin.y = bounds.y + (bounds.h / 2);
+
+    nk_widget_state_reset(state);
+
+    /* handle click and drag input */
+    if(in &&
+       in->mouse.buttons[NK_BUTTON_LEFT].down &&
+       nk_input_has_mouse_click_down_in_rect(in, NK_BUTTON_LEFT, bounds, nk_true)){
+        /* calculate angle from origin and rotate */
+        const float direction_rads[4] = {
+            NK_PI * 2.5f, /* 90  NK_UP */
+            NK_PI * 2.0f, /* 0   NK_RIGHT */
+            NK_PI * 1.5f, /* 270 NK_DOWN */
+            NK_PI,        /* 180 NK_LEFT */
+        };
+        *state = NK_WIDGET_STATE_ACTIVE;
+
+        angle = NK_ATAN2(in->mouse.pos.y - origin.y, in->mouse.pos.x - origin.x) + direction_rads[zero_direction];
+        angle -= (angle > NK_PI * 2) ? NK_PI * 3 : NK_PI;
+
+        /* account for dead space applied when drawing */
+        angle *= 1.0f / (1.0f - dead_zone_percent);
+        angle = NK_CLAMP(-NK_PI, angle, NK_PI);
+
+        /* convert -pi -> pi range to 0.0 -> 1.0 */
+        angle = (angle + NK_PI) / (NK_PI * 2);
+
+        /* click to closest step */
+        knob_value = knob_min + ( (int)(angle * knob_steps + (knob_step / 2)) ) * knob_step;
+        knob_value = NK_CLAMP(knob_min, knob_value, knob_max);
+    }
+
+    /* knob widget state */
+    if (nk_input_is_mouse_hovering_rect(in, bounds)){
+        *state = NK_WIDGET_STATE_HOVERED;
+        if (in) {
+            /* handle scroll and arrow inputs */
+            if (in->mouse.scroll_delta.y > 0 ||
+               (in->keyboard.keys[NK_KEY_UP].down && in->keyboard.keys[NK_KEY_UP].clicked))
+                knob_value += knob_step;
+
+            if (in->mouse.scroll_delta.y < 0 ||
+               (in->keyboard.keys[NK_KEY_DOWN].down && in->keyboard.keys[NK_KEY_DOWN].clicked))
+                knob_value -= knob_step;
+        }
+        knob_value = NK_CLAMP(knob_min, knob_value, knob_max);
+    }
+    if (*state & NK_WIDGET_STATE_HOVER &&
+        !nk_input_is_mouse_prev_hovering_rect(in, bounds))
+        *state |= NK_WIDGET_STATE_ENTERED;
+    else if (nk_input_is_mouse_prev_hovering_rect(in, bounds))
+        *state |= NK_WIDGET_STATE_LEFT;
+
+    return knob_value;
+}
+NK_LIB void
+nk_draw_knob(struct nk_command_buffer *out, nk_flags state,
+    const struct nk_style_knob *style, const struct nk_rect *bounds, float min, float value, float max,
+    enum nk_heading zero_direction, float dead_zone_percent)
+{
+    const struct nk_style_item *background;
+    struct nk_color knob_color, cursor;
+
+    NK_UNUSED(min);
+    NK_UNUSED(max);
+    NK_UNUSED(value);
+
+    if (state & NK_WIDGET_STATE_ACTIVED) {
+        background = &style->active;
+        knob_color = style->knob_active;
+        cursor = style->cursor_active;
+    } else if (state & NK_WIDGET_STATE_HOVER) {
+        background = &style->hover;
+        knob_color = style->knob_hover;
+        cursor = style->cursor_hover;
+    } else {
+        background = &style->normal;
+        knob_color = style->knob_normal;
+        cursor = style->cursor_normal;
+    }
+
+    /* draw background */
+    switch(background->type) {
+        case NK_STYLE_ITEM_IMAGE:
+            nk_draw_image(out, *bounds, &background->data.image, nk_rgb_factor(nk_white, style->color_factor));
+            break;
+        case NK_STYLE_ITEM_NINE_SLICE:
+            nk_draw_nine_slice(out, *bounds, &background->data.slice, nk_rgb_factor(nk_white, style->color_factor));
+            break;
+        case NK_STYLE_ITEM_COLOR:
+            nk_fill_rect(out, *bounds, 0, nk_rgb_factor(background->data.color, style->color_factor));
+            nk_stroke_rect(out, *bounds, 0, style->border, nk_rgb_factor(style->border_color, style->color_factor));
+            break;
+    }
+
+    /* draw knob */
+    nk_fill_circle(out, *bounds, nk_rgb_factor(knob_color, style->color_factor));
+    if(style->knob_border > 0){
+        struct nk_rect border_bounds = *bounds;
+        border_bounds.x += style->knob_border / 2;
+        border_bounds.y += style->knob_border / 2;
+        border_bounds.w -= style->knob_border;
+        border_bounds.h -= style->knob_border;
+        nk_stroke_circle(out, border_bounds, style->knob_border, nk_rgb_factor(style->knob_border_color, style->color_factor));
+    }
+    { /* calculate cursor line cords */
+    float half_circle_size = (bounds->w / 2);
+    float angle = (value - min) / (max - min);
+    float alive_zone =  1.0f - dead_zone_percent;
+    struct nk_vec2 cursor_start, cursor_end;
+    const float direction_rads[4] = {
+        NK_PI * 1.5f, /* 90  NK_UP */
+        0.0f,         /* 0   NK_RIGHT */
+        NK_PI * 0.5f, /* 270 NK_DOWN */
+        NK_PI,        /* 180 NK_LEFT */
+    };
+    /* calculate + apply dead zone */
+    angle = (angle * alive_zone) + (dead_zone_percent / 2);
+
+    /* percentage 0.0 -> 1.0 to radians, rads are 0.0 to (2*pi) NOT -pi to pi */
+    angle *= NK_PI * 2;
+
+    /* apply zero angle */
+    angle += direction_rads[zero_direction];
+    if(angle > NK_PI * 2)
+        angle -= NK_PI * 2;
+
+    cursor_start.x = bounds->x + half_circle_size + (angle > NK_PI);
+    cursor_start.y = bounds->y + half_circle_size + (angle < NK_PI_HALF || angle > (NK_PI * 1.5f));
+
+    cursor_end.x = cursor_start.x + (half_circle_size * NK_COS(angle));
+    cursor_end.y = cursor_start.y + (half_circle_size * NK_SIN(angle));
+
+    /* cut off half of the cursor */
+    cursor_start.x = (cursor_start.x + cursor_end.x) / 2;
+    cursor_start.y = (cursor_start.y + cursor_end.y) / 2;
+
+    /* draw cursor */
+    nk_stroke_line(out, cursor_start.x, cursor_start.y, cursor_end.x, cursor_end.y, 2, nk_rgb_factor(cursor, style->color_factor));
+    }
+}
+NK_LIB float
+nk_do_knob(nk_flags *state,
+    struct nk_command_buffer *out, struct nk_rect bounds,
+    float min, float val, float max, float step,
+    enum nk_heading zero_direction, float dead_zone_percent,
+    const struct nk_style_knob *style, struct nk_input *in)
+{
+    float knob_range;
+    float knob_min;
+    float knob_max;
+    float knob_value;
+    float knob_steps;
+
+    NK_ASSERT(style);
+    NK_ASSERT(out);
+    if (!out || !style)
+        return 0;
+
+    /* remove padding from knob bounds */
+    bounds.y = bounds.y + style->padding.y;
+    bounds.x = bounds.x + style->padding.x;
+    bounds.h = NK_MAX(bounds.h, 2*style->padding.y);
+    bounds.w = NK_MAX(bounds.w, 2*style->padding.x);
+    bounds.w -= 2 * style->padding.x;
+    bounds.h -= 2 * style->padding.y;
+    if(bounds.h < bounds.w){
+        bounds.x += (bounds.w - bounds.h) / 2;
+        bounds.w = bounds.h;
+    }
+
+    /* make sure the provided values are correct */
+    knob_max = NK_MAX(min, max);
+    knob_min = NK_MIN(min, max);
+    knob_value = NK_CLAMP(knob_min, val, knob_max);
+    knob_range = knob_max - knob_min;
+    knob_steps = knob_range / step;
+
+    knob_value = nk_knob_behavior(state, in, bounds, knob_min, knob_max, knob_value, step, knob_steps, zero_direction, dead_zone_percent);
+
+    /* draw knob */
+    if (style->draw_begin) style->draw_begin(out, style->userdata);
+    nk_draw_knob(out, *state, style, &bounds, knob_min, knob_value, knob_max, zero_direction, dead_zone_percent);
+    if (style->draw_end) style->draw_end(out, style->userdata);
+    return knob_value;
+}
+NK_API nk_bool
+nk_knob_float(struct nk_context *ctx, float min_value, float *value, float max_value,
+    float value_step, enum nk_heading zero_direction, float dead_zone_degrees)
+{
+    struct nk_window *win;
+    struct nk_panel *layout;
+    struct nk_input *in;
+    const struct nk_style *style;
+
+    int ret = 0;
+    float old_value;
+    struct nk_rect bounds;
+    enum nk_widget_layout_states state;
+
+    NK_ASSERT(ctx);
+    NK_ASSERT(ctx->current);
+    NK_ASSERT(ctx->current->layout);
+    NK_ASSERT(value);
+    NK_ASSERT(NK_BETWEEN(dead_zone_degrees, 0.0f, 360.0f));
+    if (!ctx || !ctx->current || !ctx->current->layout || !value)
+        return ret;
+
+    win = ctx->current;
+    style = &ctx->style;
+    layout = win->layout;
+
+    state = nk_widget(&bounds, ctx);
+    if (!state) return ret;
+    in = (state == NK_WIDGET_DISABLED || layout->flags & NK_WINDOW_ROM) ? 0 : &ctx->input;
+
+    old_value = *value;
+    *value = nk_do_knob(&ctx->last_widget_state, &win->buffer, bounds, min_value,
+                old_value, max_value, value_step, zero_direction, dead_zone_degrees / 360.0f, &style->knob, in);
+
+    return (old_value > *value || old_value < *value);
+}
+NK_API nk_bool
+nk_knob_int(struct nk_context *ctx, int min, int *val, int max, int step,
+    enum nk_heading zero_direction, float dead_zone_degrees)
+{
+    int ret;
+    float value = (float)*val;
+    ret = nk_knob_float(ctx, (float)min, &value, (float)max, (float)step, zero_direction, dead_zone_degrees);
+    *val =  (int)value;
+    return ret;
+}